Significant other’s kinks

So I’ve been dating this guy for a year now and our sex life has been up and down. It’s mostly been vanilla with a little spice thrown in occasionally because we both live at home right now and it’s kind of hard to do anything when people are home. I like it rough, I like being choked and tied up and forced into submission. My boyfriend does this to me some times but not all the time. I’ve noticed I’ve had to take on a more dominant role in my relationship which is okay but I’m more of a sub. Anyway, so I was going through his phone cuz I just had a feeling I needed to go through it. The two times before this that I’ve had this feeling, I caught him flirting with other women. We talked about it and the issues were fixed and he’s been really good and we’re moving in together this weekend but I felt like I needed to go through his phone. So I just went through his phone and found like a couple things that were iffy with these two girls who are friends and he’s known them for a while. Longer than we’ve known each other. But with one of them, he had previous sexual relations with but doesn’t anymore cuz he’s with me and she’s got a new mans. Anyway he told her he’s been thinking about opening up to me about his MDLB (mommy dom little boy) and diaper fetish.... i had no clue what the hell he this was until I looked it up. I am in no way shape or form into this stuff and I don’t understand it. I don’t shame anyone if you’re into that stuff, like that’s your thing, you do you. He has no clue that I know and the last thing I want to do is accidentally shame him or put him down about it because I wouldn’t want someone to do that to me. It’s a very vulnerable and sensitive side to him and I don’t want him to feel like he can’t open up to me about stuff like that. I want him to be open to me about this stuff and sure I’m into trying new things but idk if I can get behind this. I remember he had told me that he had showed his ex stuff that he was into but didn’t specify what it was (which I’m assuming is this) and she shut him down fast which is why he hasn’t told me about it yet. I honestly don’t know what to do right now. I love him so much but I’m honestly scared that I’m not gonna be able to satisfy his sexual desires and he’ll just one day leave. But at the same time like my deepest fetish that I’ve ever told anyone and not even him is I like being forced to do stuff. So do I tell him this in hopes that he’ll come clean about it? How should I react when he actually feels comfortable enough to tell me? How do I handle this? Cuz I don’t know what the hell im doing and getting myself into.