Hi BigBoy! Be sure you have your stoma measurement right. You don't want your wafer sitting on top of your stoma even a little bit because stool will get underneath. If your stoma is between the standard pre-cut sizes choose the size up and use a ring to fill in the small space. Again make sure the ring is not on top of your stoma. If you have a steady hand you might like a cut to fit. All of the previous mentioned suggestions still apply.
If your peristomal skin is irritated and itchy and burning you might have a fungus infection. Try some 2% miconozole powder. It won't hurt anything to try it.
For weepy skin domeboro soaks help dry it up so your wafer will stick but it won't heal anything.
Make sure you wash your hands with antibacterial soap before handling any of your supplies.
There are so many things that can cause your problems. I had quite a journey myself. I found out I was allergic to the adhesive remover I was using and some adhesives. Yeah! Because our main objective is good adhesion I had quite a journey finding wafers, extenders, etc that I wasn't allergic to. Even stoma powder which is an adhesive. I still have problems. I don't try to keep my wafer on once it starts leaking underneath, I change it. Doesn't matter if it's the same day because stool is extremely irritating.
Bottom line is it's not just the fit of the wafer if there are underlying issues.
I'm sorry that you're going through this. You probably don't want to make a lot of changes all at once because you won't know which thing you changed is working for you.
God bless and good luck! E& I