Please I need some advice about my boyfriend ...?

I felt up my boyfriend and he's much bigger then I thought he would be, and now I'm kinda scared because he asked me if I would be comfortable giving him a hand job soon. I said I'd think about it, but I dunno how I feel about doing stuff like that. I'm a little late to this stuff (I'm 23) I'm waiting until marriage until I have sex, mostly because of being raised in a christian environment, but they never covered oral so I've never really thought about it. but I never realized how big some guys were and now I'm kinda scared both because of his size and that I might have initiated something that I'm not sure I'm ready for, but I'm also not sure if I'm not. I really actually want to ask my mom what she thinks about oral (we're pretty close) but every time I bring up my boyfriend shes all like "I don't want to hear it" or "I don't wanna know" so I haven't asked for her advice yet, but I think she thinks we're already doing stuff like that (we've been seeing each other since February) I'm just so lost, please any advice on any of this is greatly appreciated