A convex is designed with a bubble around the stoma hole to provide downward pressure (with the help of a belt) around the stoma to force it up and out more and to assist those with belly folds right where the stoma is.
Unfortunately the bubble is often stiff but can be weakened horizontally to fit a little more snuggly in a belly fold.
You shouldn't be feeling any pain from the convex itself, rather you have a leak at the top and bottom and digestive enzymes are eating your skin causing pain.
Convexes are used for near flush stomas and belly folds mainly.
I have the same problem and I don't have a fool proof easy method but can set you on your way.
When cleaning the stoma area in the shower, use liquid antibacterial soap only and after each spewing if it occurs.
Once stoma has quieted down, blow dry the area well. Apply nothing.
Go lay down on your back, have fresh dry toilet paper available to dab up moisture and stoma spew, but if it gets on the skin you have to wash the area with soap again as spew contains oils and will make putting the adhesive paste on impossible. You need clean, dry, oil free skin so the paste will stick.
Cut your wafer hole to match the shape of your stoma and just a tiny hair bigger. Test fit and make marks on flange edge of wafer and your skin to match up to later.
Weaken your wafer bubble horizontally some so it bends and is curved a little bit.
Use no sting paste and mix in a tiny bit of stoma powder to get it to activate. Spread a thin coat around the stoma to about 1/2" out, same size as your convex bubble. Focus on wounds first so to ensure it sticks, if not remove and discard wet paste and blow dry and try again until it does. This method avoids wasting paste, rings and wafers. Use a flat type stick to apply paste as it will stick to fingers and everything else. Wipe off stick using toilet paper and discard.
Dab the stoma, never wipe wet or press hard as the stoma is fragile and will bleed easily, making putting a bag on nearly impossible until it stops bleeding.
Next put two rings of no sting paste around the stoma about 1/3" away from it. Score two groves in the top of the paste rings and put some stoma powder in there and mix it in some.
Peel backing off wafer and apply, gently pressing down and pressing adhesive flange onto the skin and hold. If done right the paste shouldn't be covering the stoma, just appears around the edge of the inside hole.
Apply extra large barrier strips all around centering over the wafer hook area (and under the hooks) and meeting at the bottom. Top can have a small gap you can fill with another cut piece.
Now you need to wait awhile, even a few hours sometimes, on your back, for that paste to properly set up. If you go vertical too quickly with unset paste it runs out and leaks. Adding stoma powder into the paste will make it set up faster.
After awhile the paste will set up and feel rubbery or hard through the appliance, not soft or squishy. Now apply your belt with a gentle pressure.
Sleep only on your back with the back slightly elevated and a pillow under each arm to train yourself to stay on your back. Rolling on the left side causes blowouts and on the right causes graneoluma because the wafer digs into the skin. It's the belt doing it, why you need to remain sleeping on your back.
Eat only foods that turn into liquid upon exit of your stoma.
[b]Signs of a clogged stoma.
[/b]
No output or only watery output under pressure for a few hours after eating. Could be caused by a covered stoma by improper application of an appliance, typically hole is cut too small or too much paste. Also could be caused by eating hard food. Seek treatment by an emergency room, remove appliance if necessary and wait. If clogged a severe pain will eventually appear which hopefully will clear itself. If not a trip to surgery would be necessary. Unfortunately very high and frequent output will ensue after clearing for quite some time which will likely making putting on a replacement appliance difficult. Use stool thickening tactics (below). If going to an ER, bring your own otosmy gear and a change of clothes as hospital likely doesn't carry or doesn't know how.
[b]What is "pancaking?"[/b]
Pancaking occurs when a vacuum in the bag (likely do to a clogged filter) or super thick stool blocks stool from depositing to the bottom of the bag. Thus can force bag off and cause leaks. Controlling what one eats and by mixing and consuming stool thickening and stool softening foods at the same time to get a balance.
[b]What is "ballooning?"
[/b]
Ballooning occurs when foods eaten produce too much gas and the filter gets clogged (likely due to laying down) and thus forces bag off and causes leaks.
These two conditions can cause premature bag replacement and leaks which burn the skin. It's better to replace the appliance if there is any continuous stinging pain, don't just live with it. Keep an eye on your otosmy supply and have ample reserves.
I've found that caffeine, in coffee, tea and even chocolate causes diarrhea and can assist in controlling flow so stool is more liquid..however coffee makes output very acidic making burns worse. Dried Chinese Crispy Noodles, Cheerios or applesauce (peeled apples) are the exact opposite, a stool thickening food. By mixing these with other foods one can manipulate their stool output and counter the issues above. Also the severe thickening helps in cases where one has severe diarrhea and unable to reattach a new bag due to high flow.
[b]Eating Guide
[/b]
Partially copied from my nutritionists guide. Ileostomy Nutrition Therapy from the Academy of Nutrition and Dietetics. (This handout may be duplicated for client education.)
My recommendation is to see a nutritionist for the full guide as not all can be pasted here
I've added my own observations to further clarify
Chew all foods well to the consistency of paste.
[b]Foods That May Cause Blockage (very bad avoid!)
[/b]
Apples, unpeeled (unpeeled and applesauce are excellent thickeners, don't eat the core, chew well)
Bean sprouts
Cabbage, raw
Casing on sausage (inside fine if no tough parts, avoid swallowing if a chunk is felt)
Celery (avoid)
Chinese vegetables (stir fried crunchy, too hard, need soft veggies with no skins)
Coconut
Coleslaw
Corn (grits also, corn anything doesn't seem to dissolve in stomach)
Cucumbers (skins bad, inside chewed up good seems okay, no seeds)
Dried fruit, raisins
Grapes
Green peppers (red, yellow also) pureed or very very small seems okay in small amounts
Mushrooms (doesn't dissolve in stomach) pureed or very very small seems okay in small amounts
Nuts (totally avoid)
Peas (mushy interior okay, like pea soup, skins a problem)
Pickles (skins a problem, inside if chewed up good seems okay, seeds not)
Pineapple (liquid okay, mushy parts fine, hard parts not, tricky)
Popcorn (totally avoid)
Relishes and olives
Salad greens (diarrhea nightmare too)
Seeds and nuts (avoid)
Spinach (doesn't digest, pureed perhaps)
Tough, fibrous meats (for
example, steak on grill, well done, tough parts especially)
Vegetable and fruit skins, (any avoid)
Whole grains (no grits, oatmeal seems to be okay, Cheerios is an excellent thickener)
[b]Foods That May Cause Gas or Odor
[/b]
Alcohol
Apples
Asparagus (stink)
Bananas
Beer
Broccoli (clog hazard)
Brussels sprouts (clog hazard)
Cabbage (clog hazard)
Carbonated beverages
Cauliflower
Cheese, some types
Corn (clog hazard)
Cucumber
Dairy products
Dried beans and peas (clog hazard)
Eggs (don't digest in stomach)
Fatty foods
Fish (cooked salmon in small portions may not, nor stink)
Grapes
Green pepper (red and yellow also, clog hazzard)
Melons
Onions (clog hazard)
Peanuts (clog hazard)
Prunes
Radishes
Turnips
Soda and sipping using straws, (drink from glass instead)
Seafood (oh God does it stink!)
If your having pancaking issues a small amount of something above (like having a soda during a meal) could introduce some air into your diet and thus into the bag. Also by avoiding too much thickening foods by themselves which often contribute to pancaking.
[b]Foods That May Help Relieve Gas and Odor[/b]
Buttermilk
Cranberry juice
Parsley
Yogurt with active cultures (Greek yogurt)
[b]Foods That May Cause Diarrhea (looser or more frequent stool)
[/b]
Alcohol (including beer)
Apricots (and stone fruits)
Beans, baked or legumes
Bran
Broccoli
Brussels sprouts
Cabbage
Caffeinated drinks
(especially hot)
Chocolate
Corn (in my experience corn anything doesn't digest in stomach, just passed through and out, kernels/popcorn will clog)
Fried meats, fish, poultry (KFC, supermarket rotisserie chicken very bad, anything soaked in brine)
Fruit juice: apple, grape, orange (small amount okay)
Fruit: fresh, canned, or dried (small amount okay)
Glucose-free foods containing mannitol or
sorbitol
Gum, sugar free
High-fat foods
High-sugar foods
High salt foods (KFC, supermarket rotisserie chicken)
High seasoned foods (blackened)
Licorice
Milk and dairy foods (small amounts okay)
Nuts or seeds (bad, clog hazard)
Peaches (stone fruit, one rarely okay)
Peas
Plums (stone fruit)
Prune juice or prunes
Soup
Spicy foods
Sugar-free substitutes
Tomatoes
Turnip greens/green leafy
vegetables, raw
Wheat/whole grains
Wine
Rice (1/4 cup in mixed in food okay), refried beans (1/4 cup okay) pasta (one cup max).
Any foods soaked in brine or fried (rotisserie chicken, Kentucky fried chicken etc)
[b]Foods That May Cause Diarrhea (looser or more frequent stool)
[/b]
Alcohol (including beer)
Apricots (and stone fruits)
Beans, baked or legumes
Bran
Broccoli
Brussels sprouts
Cabbage
Caffeinated drinks
(especially hot)
Chocolate
Corn (clog hazard, even grits, doesn't digest)
Fried meats, fish poultry
Fruit juice: apple, grape,
orange
Fruit: fresh, canned, or
dried
Glucose-free foods
containing mannitol or
sorbitol
Gum, sugar free
High-fat foods
High-sugar foods
High salty foods
Licorice
Milk and dairy foods
Nuts or seeds
Peaches (stone fruit)
Peas
Plums (stone fruit)
Prune juice or prunes
Soup
Spicy foods
Sugar-free substitutes
Tomatoes
Turnip greens/green leafy
vegetables, raw
Wheat/whole grains
Wine
Soylent nutritional drink
[b]Foods That May Help Thicken Stool
[/b]
Applesauce (unpeeled apples, no cores)
Bananas
Barley (when OK to have
fiber)
Cheese (cheese food may be a clog problem, use real cheese)
Dried Chinese Crispy Noodles (severe thickening, mix with other food that causes diarrhea)
Marshmallows
Oatmeal (when OK to have
fiber)
Pasta (sauces may increase
symptoms) (in my experience more than a cup of pasta causes diarrhea)
Peanut butter, creamy only, nuts clog (makes skin oily)
Potatoes, no skin (skin clogs, more than a cup causes diarrhea)
Pretzels (salty may cause more flow water consumption)
Metamucil, mix or crackers (mix in cup of water and drink before it gells up)
I'm adding to this list based upon experience.