My wife found out last year when she found a pack of nappies in the boot of my car. I had to come clean and she took it very badly at first. She too didn't want to think of her man in nappies. I have a professional job, I play a lot of sport, go to the gym etc and it's something she can never imagine me being into. She knew about the fact I wore nappies/pull ups quite late as a child and the issues I had growing up using the toilet but had no idea this led to my love of wearing nappies. The thing that bothered her most was the fact I hid it from her for so long. She started to question what else I had not told her over the years (we've been together for 14 years) and said that maybe she didn't know me at all. We had numerous conversations over the following weeks and I told her about how it helps me deal with stress and anxiety etc. She still doesn't understand it, and probably never will. She has made it clear that she doesn't want to see me wearing, doesn't want me to wear around her and doesn't want to see any nappies in the house. She does however now somewhat accept that it's something that I enjoy, and something that has been a part of me for so long it's not something I can simply give up. At first she did mention maybe I should see someone about it, like a therapist as I think she wanted "to cure me" but she hasn't really pressed this subject since. Now she knows that when I'm home alone I'll often wear but I'll change before she gets home so she doesn't have to see. She never asks about it, or even mentions it and I think for her "its out of sight, out of mind". For me this is somewhat of a win, as I can continue as I always have but at the same time I'd like her to be more accepting. I don't expect her to be involved in any way, but maybe just be open to discussions about it and not simply ignoring it.
I think if she ever asked me to stop and gave me an ultimatum I'd find it really difficult as it's something that has been a part of me for so long... I'd like to think it would never happen but if she can't accept me, including my kinks and flaws then I'd certainly start to question our relationship.