My girlfriend can't orgasm!

There's nothing wrong with that... maybe there is, i don't know.. truth is i've never had an orgasm until recently, and i can't have one with my boyfriend at all, it has to be self-induced.
i really envy the women who can reach it with their boyfriends, but it's not the boyfriend's fault.
ask her what she likes, how she likes to be touched..
good luck bro.
(still waiting for that man who will make me reach heaven and back:)

most woman don't have orgasms during sex. figure out how she "works" through oral or fingering first if you want to try to bring her to orgasm.

I agree with oz. You need to do some exploring, my first was not through sex, but don't give up! Find out other things that get her aroused which may help.