Try the Coloplast Extended Wear Convex Wafer...I had problems with the Convatec wafers w/convexity (not adhering well) and had a sample of the Coloplast so I gave it a shot...I was amazed at the difference.
Have you seen your WOC Nurse since the weight gain? You may be dealing with a combination of ulcers and weight gain causing issues
Last thought would be to have your stoma moved to the other side...sometimes ulcers just don't heal while covered
Sorry you are going through all of that! I am sure someone else will be along with more suggestions.