Boyfriend uncomfortable with BDSM *EDITED*

I’m really into BDSM especially pet play. I love to be treated like a cat and I’ve always wanted the full experience: being collared and leashes, commands, etc. But when I brought this up to my boyfriend he said no. I asked him why and he said “Because you’re my girlfriend.” I get that he means he doesn’t want to treat me like an animal because he respects me, but that’s literally what I love and what I personally WANT him to do. He also is uncomfortable with choking and slapping me during sex, two of my absolute favorite things. He’s said since we met that he’s down to try kinky things but the most he ever wants to do is tie me up/handcuff me. He’s not open to any of the kinky things I want to do. How do I go about easing him into it? I know I can’t force someone to do things they don’t want to do, but I at least would like him to try and he absolutely won’t.

*EDIT* It’s not a deal breaker. I’m in love with him, I see myself getting married and having children with him. The sex is amazing with or without BDSM. It just makes me sad that he’s so closed minded to the things I’m into. He doesn’t even consider himself a dom because he’s never done anything related to BDSM. It’s something completely new to him, which is why I’m saddened by the fact that he’s not open to trying. Like, how does he know he’s not truly ok with it if he’s never tried? And also, how can he say he’s open to kinky things but then shut down all my ideas?