Sounds like your wife might never have fully accepted it, more like just tolerated it, and even gave it an honest try?
Does your ability to have sex and achieve orgasm depend on wearing diapers and pads? If so, she might feel substituted for. Do you ever have sex w/ her just straight up with no fetish items? If so, when was the last time?
What about giving her a night where she gets to act out her desire, maybe some kind of role playing?
I guess what I'm saying is to throw her a bone so she has sex with a MAN once in a while. Not saying this to offend you, as I love getting all sissy/girly myself, but women usually are attracted to that masculinity that they see/sense when they first developed urges to be with us. Ripping that away some time into the relationship and not giving it back is a tough pill for anyone to swallow. Coming her way might let you still have fun with your fetish in the relationship. Maybe a couple nights a week where she can reach across and grab a naked hard cock as opposed to a diaper or pair of panties once in a while. Letting her get you off, with nothing more but her body and desire will make her feel like a desirable woman.
Having this fetish is like a separate sexual preference, and is very difficult to deny. If she completely rejects it, I can see this leading to divorce as it is shutting down your "preference". But if you give her what she needs a few times a week, and if she feels that you did, then maybe there's hope...