I think this is everyone's biggest fear, and the reasoning behind both keeping it a secret indefinitely, and telling someone too soon, both of which are mistakes.I was married 10 years before my Ex found out. She pitched a fit, and not about me keeping a secret for 10 years. She found it very disgusting in her words, and that I was a pervert. I ended up moving out 18 months later, as the relationship was never the same again.
I have not told my boyfriend of four months about it, and I'm not sure if I will. People keep telling me this is a mistake. My recent near-discovery, where I had the diapers hidden in a transparent container under the bed and he and I had to pull everything out to get to my cat, seemed to back up that belief. But my desire to wear seems to be fading and has been for the past three years. Most of the time I have no interest in wearing, and sometimes I wear because I have the mindset "jeez, I have to get rid of these diapers eventually" more so than because I want to. So I feel like I can get away with never telling him if I'm not going to be wearing much anyway.
I've told two previous boyfriends. One of them babied me once, the other one never did because although he said he accepted it, he clearly wasn't crazy about the idea. I wouldn't exactly say I regret it, but the feeling of going through all the emotional upheaval of telling someone, thinking "this could be the person I might spend the rest of my life with, better tell him!" and then it doesn't work out and I feel like I told them for no good reason...well, it kind of feels like you might feel if you trained for an athletic event for a few weeks only to then be told that you couldn't participate in the event and all your training was for nothing.
Plus, when you tell a boyfriend/girlfriend of several months or even a longer period that you are an AB or DL, you are doing so with a certain amount of trust and an assumption that that trust will always be there. But you don't know that it will or that all that trust will always be there even if you part ways. People do change, and unfortunately sometimes for the worst. And even if they don't change permanently, the temptation to tell a mutual friend some juicy gossip about you in the aftermath of a bad breakup might prove too much. I sometimes wonder if my first boyfriend didn't tell a mutual friend of ours who he wound up dating a few months after he and I had broken up, but fortunately I've never seen any indication that he did.