I can't cum when I'm with my boyfriend???

I've been with my boyfriend for about 3 years now (we were 15 at the time) and we've been sexually active for about a year. We're a little bit long distance so it's not like we see eachother all the time but as we get more into things I've found that I can't have an orgasm. He doesn't last very long during sex (it's not a big deal, I get why) so it's not like I could by that. When he rubs my clit it feels good but don't think I could orgasm from it, and when he legit fingers me it feels amazing and makes me moan a little but I still don't cum and I feel really bad. He'll eat me out once in a while but normally not for longer than a minute or so at a time so nothing really happens. I make him cum super easily and he told me once that it kinda makes him feel bad that he can't do the same for me. I told him not to worry about it and that it wasn't his fault at all but I seriously don't know what's wrong with me. Does anyone else have this problem? Will I ever be able to cum with him? I love him so much and just want it to happen:( When I masturbate (I use a vibrator) I have no issue, so what's up with me?