Hello and welcome.
I'm assuming you have a colostomy. I had hernia repair mesh migrate and puncture my colon. So I have a colostomy too.
My stomach looked like heck after surgery. Took about 4 months before it started looking better/smoother.
What company makes your wafer/flange? I use Hollister 2-piece system.
I'm a small guy, now at one year post-op. Haven't had adhesion trouble.
I go 7 days between wafer changes (every Sunday) and change bags 2-3 times a week. I shower with wafer/bag off. Water and soap will not hurt your stoma. Use soap that has no lotions, fragrances, or color. These chemicals will interfere with wafer adhesion. I use Cetaphil soap. I also don't let shampoo/conditioner wash down the front of my stomach when I rinse. Pat skin around stoma dry, don't rub. Be careful you don't brush stoma with towel edge. Stoma bleeds easily. Peristomal skin (around your stoma) must be dry and chemical-free for best adhesion. Clean stoma in shower with wet paper towel...gently. Take a paper cup or paper towels in shower to catch any output from stoma.
During the week I shower with wafer/bag on (put on new bag first). I use a handheld shower head and avoid directly wetting the wafer/bag. After drying off, I remove the bag, wipe with paper towel, then use a blow dryer set on low to dry it. Don't use toilet paper on your stoma, only wet paper towel.
Putting on a wafer after removing the old one:
Use adhesive remover wipe, carefully wipe around stoma. Use finger to test skin around stoma, lightly press on skin/lift. You're looking for stickiness from old adhesive. If still a little sticky, wipe again with adhesive remover.
Cut hole in wafer to fit around stoma. Leave about an 1/8 of an inch gap all around stoma. Grab wafer, press and hold the flat side against your stomach or leg for a minute to warm it up. Pull off plastic backing, place wafer on stoma. Use both hands, gently press on wafer for a minute. Change hand position, press again. Use blow dryer set on low, blow on wafer for a minute. If using a 2-piece system, snap on bag. I then put on an ostomy support belt for an hour.
If you continue to get leaks, your skin might be uneven. There are moldable barrier rings you can use to create a flatter surface for the wafer to sit on. Ring goes on skin first, then wafer on top of it. Ring can be fitted right up against your stoma. Wafer hole can be cut a little bigger. Ring seals around stoma, wafer seals to ring.
Good luck, let us know what happens.