After having had several relationships in my teens/early 20s--a few of them lasting several years--I realized while I was still single that I'd never be able to get married unless my wife knew about and accepted my diapers.
During my late teenage years I had one girlfriend--starting in high school, followed by a few years apart, then back together for another year or so when I was 20--who was very liberal-minded and fun in bed (if I made her come hard enough she'd squirt pee all over me which was wonderful). But she absolutely could not stand the idea of diapers. She was always talking about how she would never have kids because she absolutely was NOT going to deal with having to change their diapers! So I figured out very early on--without even having to bring up the notion of ME wearing the diapers--that she just wouldn't do over the long term, and broke up with her. (And I still feel kind of bad about this, at the time she really did not understand why I was doing this, but I decided I couldn't just come out and tell her "Because I love wearing diapers and your attitudes have shown me that you'll likely never accept this part of me.")
Then I spent about four more years dating another girl who, at first, was fine with me and my diapers. This, because she otherwise refused to have sex with me. She wanted to "save it for marriage". So I spent a couple of years enjoying openly wearing my diapers around her. Then she finally decided to try sex, and at that point it was time (according to her) for me to give up my diapers. It was "Now that you have this, you no longer need THOSE." This was one of several factors leading to our breaking up. (Time would reveal that she was a latent lesbian so this never would have worked out, with or without my diapers). As bad as this was near the end, I must say that it convinced me just how much I loved my diapers. There were many nights where we'd have a big argument, I'd walk out, get in the car and leave, and on the way home I'd stop at the store and buy a box of toddler-sized Pampers then half an hour later there I was, back in my diapers. (I then decided that "Girls come and girls go but I'll ALWAYS have my diapers!")
There were other relationships where I hinted at it, to no avail. Some where I knew there was no chance of it ever happening but decided to date the girl a while anyway for the other "benefits". But by the time I was 25 I realized that I'd likely end up being single because I couldn't marry anyone who didn't accept my diapers, and I'd probably never find a woman who did.
And after accepting that, I DID find one. But I didn't know this until the relationship started to get serious and decided "OK, it's time to be honest about this" and told her "If we're going to go farther with this there's something you need to know about me." I think she was expecting to hear something horrible (I have some incurable disease, I worship Satan, etc.) I was scared to death but finally got it out... "I'm into wearing diapers, I always in one way or another have been, and I always will be." And she sighed with relief "Oh is THAT ALL?"
Over the years we've had our ups and downs but she's always known of and accepted that I'm going to wear my diapers when I need to wear my diapers. I don't keep them out in the open for visitors to see but I also don't have to hide them from her or worry about her finding them. At times she has very much enjoyed participating and other times, not so much. But it's the honesty that counts.
So, bit of advice #1: If you're single, don't marry anyone without first telling them about your diapers and giving them the choice of accepting it or not (then whatever the decision, proceed from there).
#2: If you knew you loved diapers, didn't tell your fiancee, got married anyway, then she found out later, well, if she's angry about it, I don't blame her. I'm not sure you can fix that situation, unfortunately. Good luck.
#3: If you've discovered SINCE you were married that you love diapers, be honest about it, explain that it's a new interest and source of pleasure and explain how you discovered it. Tell her you'd love for her to participate but if she doesn't want to, that's OK. But ask if it's OK for you to do it anyway, if she doesn't want to be involved you can keep that part of your life to yourself. Just be sure to offer her something in exchange for it--shower her with love and affection and make sure that SHE is sexually satisfied (whether this involves your diapers or not).