Actually, we need more insight. Okay, so, your girlfriend doesn't have orgasms from vaginal intercourse/stimulation? So, what positions have you tried, what are her favorites, have you added in some stimulation to the clit while having intercourse? Everybody is different, I've been with a girl that from straight vaginal intercourse would usually have 3-4 orgasms and as many as 7 or 8 by the time I would climax. I've also been with a girl that typically didn't have orgasms from only vaginal stimulation - so - on her belly with me hitting it from the back and reaching my hand around her under her belly and playing with her clit or her on top and me gently rubbing her clit did the trick. Anyway, we need much more insight to be able to adequately answer the question.
I've heard it described that a woman having an orgasm is kind of like a dog trying to scratch it's back - sometimes a little help is needed if you are picking up what I'm dropping.
my .02