Sounds like my stoma exactly.
Okay, you're likely going to need a one-piece convex, stoma adhesive, skin protectant, no-sting paste, extra-large barrier strips, and an ostomy belt.
First, wash the area in the shower using antibacterial dish soap to sterilize burn wounds. Then use moisturizing soap after that. Wait until any stoma spewing stops. Final wash and rinse.
Pat dry using soft dry toilet paper, do not wipe on stoma or it may bleed. Only dab dry.
Use a blow dryer to get the area bone dry until it's rough skin.
Use stoma adhesive just around the stoma in very small amounts (and on any weeping damaged skin) and dry brush remove until it's gone. It will leave an invisible coat.
Cover the adhesive area with skin protectant (I use generic Flonase as it stops the sting) and blow dry well, repeat.
Cut the wafer hole to be just a hair bigger than your stoma, if it's oval cut an oval. Test fit.
Now apply no-sting paste tube around stoma and spread out to 1/2" away from stoma and of course next to it. If you dried well, it should just stick with no problem. If not, remove and fix the issue above.
Now peel backing off convex and the flat area out another bead of paste. Gently press into place and watch that you're lined up correctly with stoma. Press just enough that paste appears in the wafer hole edges evenly all around. Do not press down hard or it just squeezes the paste out.
Allow paste to harden up to form a wall of sorts around stoma. Push wafer flanges down to meet skin.
Put extra-large barrier strips all around and lay on your back for a few hours while the paste sets up, then put on the ostomy belt to give gentle downward pressure.
Sleep only on your back using pillows under each arm. Eat only from AM to about 2 PM, then only small snacks until morning. Avoid skins or tough vegetables and hard meats. No nuts or seeds. Only mushy type foods. Avoid alcohol. Avoid foods that cause runaway diarrhea.
It takes time to learn this process and even years to perfect sometimes, and everyone's body shape is different.
If you have scar tissue, I've learned that just putting a tiny bit of coconut or olive oil-based skin lubricant on the scars will keep them from getting itchy by the adhesive.
Take a hot shower only on bag change days, washcloth bird baths in between because sweating causes the bag to come off.
With a one-piece, you flush and rinse from the bottom on the toilet using a small water bottle and some antibacterial dish soap. This one-piece doesn't disturb the seal as much as a two-piece does. I've made my one-piece last up to 7 days; by then the wafer is usually toast anyway so the whole mess comes off. One piece is usually less expensive as well.
Changing the wafer every 5 - 7 days is normal for seasoned ostomy folks; several times a day is usually only in the case of newbies with scabs and other issues with skin.