Yes, your stoma needs to stick out more. It is not a big medical procedure to have it done. I would recommend you look into it right away. Your skin will progressively get more irritated. Replacing the wafer too much will also cause lots of skin damage. And in your situation, you'll be constantly changing the wafer due to leaks.
The "dimple" can be sealed using a piece of barrier ring or barrier material. Barrier material is available in a flat, square sheet (you then cut out a piece to place over the dimple, then install wafer). Also, it's sold in crescent shape (like a quarter moon in the sky).
All ostomy supply manufacturers offer free samples. Try out a 1-piece system, different 2-piece types, and different barrier rings. It takes a while to find the system and products that work for you.
Try out skin barrier products. I use 3M Cavilon spray and swabs. Once your peristomal skin (skin surrounding your stoma) is clean, and most adhesive residue removed, you now spray on, or use swabs/wipes, barrier film. I spray Cavilon all around my stoma. The stuff doesn't hurt stomas, so no need to be careful. Don't put on too much, just need a thin film. Let it dry. Now you're ready to cover the dimple with barrier material, or put on a barrier ring, then wafer.
On my wafer change day, I remove everything, take a shower using Cetaphil soap (do NOT use soaps containing lotions, dyes, or fragrance). It's OK to soap up the area around your stoma; water and soap won't hurt it. You can even soap up the stoma itself, though in your case it's nearly recessed into your skin. When you wash your hair, don't allow the rinse water to flow down the front of your stomach and around the stoma. Eat a couple of marshmallows before you shower; it will slow down output. Bring in a couple of paper cups to catch any output. Only clean your stoma with a wet paper towel, gently. Never use toilet paper. Shower complete, pat the area around your stoma dry, don't rub.
Retry convex products, but add an elastic support belt, which will help push the convex down.
There are different kinds of elastic belts.
Thin width, bag retention belts. They clip onto bag tabs. Used with 2-piece systems. These won't help with "push down," but will secure a heavy, full bag from popping off suddenly. I wear a Hollister one of these all the time.
Wider hernia support belts have a plastic ring that pushes down on the wafer/bag flange, maintaining constant, consistent pressure. They have Velcro closures to easily adjust the pressure. This type of belt also pushes in peristomal hernias. I wear one of these when going on long walks/bike rides or performing any exercise. I also have the same type of belt with a "prolapse" strap. This strap goes over the bag, slightly compressing my stoma. It has a Velcro closure to adjust pressure. I wear this to church or going out to dinner. It makes my peristomal hernia/stoma far less noticeable. These types of belts are available in widths from 3 to 8 inches. I'm a little guy, so I have a 3 and a 4. These types of belts would secure a convex wafer down around your stoma. I use Nu-Hope Corporation belts. They have an excellent selection with lots of customizing options. They are located in Pacoima, Calif., USA. I order them from my ostomy supplier: EdgePark. Amazon has many belts available, fairly cheap. I've ordered many different ones to try out.
There are also belts to secure a stoma during sporting activities. One major manufacturer is "Stealth Belt."
For swimming, there is a belt called StomaGoggle. Mainly used to keep wafer and bag dry during a shower, but comes in handy for other gentle water activities.
Most important, get revision of your stoma. It should stick out at least 1 inch. Better too much than too little.