18 year old male can't ejaculate with girlfriend, whats wron

Ok I'm 18 and I have a problem, like by my self I can masterbait and ejaculate just fine but when I'm with girls. I just can't. I haven't had sex yet but I have recieved oral sex from a few girls and I just can't ejaculate. The longest I've gotten oral sex was about 10 minutes, is there a problem with me? Should I go to a doctor? Is it just that Im not really into oral sex? Help me out please.

you da man.
but no, seriously; it's probably just that either a) the girls giving you oral sex aren't exactly pro at it, or b) as you said yourself, you just aren't so into it... once you actually have real sex, then one of two things will be the case 1) you will last forever. which is pretty wicked. or 2) you'll pop in about 2 minutes; which is what happens to most guys the very first time anyways.