He keeps asking for a blowjob

My 18M bf keeps asking for a blowjob. We've had sex, I've given him handjobs, and he fingered me. I'm not scared about doing it wrong because, all in all, it can't be that difficult to do, but something about it I'm just not ready for. I don't know if it's because I'm not horny, so maybe that's why I'm not like into doing it? because I'm not horny, I'm just not horny, so I'm not into doing it? I'm also just nervous, in general, about having a dick in my mouth. Like, I don't have a gag reflex, so I'm ok in that aspect, but he keeps like genuinely begging. He brings it up almost every time we hang out, and it makes me feel a bit pressured ngl. I know he doesn't mean it like that, and I know if I just flat out said no, I don't wanna do that, he would force me to or anything. But I do fear that if it's something I don't do he will break up with me. What do I do??