My husband has had an ostomy since May 2012 and has had terrible problems! His skin is so sensitive and we tried everything imaginable! The only thing that finally worked was Hollister products, but even then he had to change it every day. He also had to put VERY THIN layers of a couple different anti-fungal and anti-itch creams and powders under his wafer. And there's only one kind of barrier film we've found that doesn't also cause him to break out.
Now he has a temporary loop ileostomy which is even worse because they created a crease under the stoma somehow and it's sunken in. Because he now needs a deep convex, he had to switch to a Marlen one-piece, but the tape drives him nuts within minutes! At our last CC visit, the stoma nurse suggested Coloplast Brava Skin Barrier strips. They stick to the appliance tape and then to him so the tape doesn't actually touch his skin. It helps alot, but still, after a day, he's itchy again.
He also has to stay out of all heat & humidity, because that makes the itching even worse. 5 more weeks. He just has to make it 5 more weeks and he'll finally be free of it! I'm so happy for him.
I hope you figure something out soon! The time period where you can't find something that works for you is miserable.