A few Q's on orgasm times

My girlfriend and I are active with foreplay, but not actual intercourse. When I start to do anything to her that should evoke an orgasm (oral or fingering), she has her orgasm within about three to five minutes. Very quickly. Which she doesn't mind but she does wish that the feeling would go a little longer for her.

When she tries to make me feel good, oral usually doesn't do it (for some reason it hurts . . . I have a suspicion that some teeth are gettin in the way so I avoid her giving me oral), so we usually resort to a tried and true method of her hand and vaseline. But for me it will take anywhere from an hour to three hours. Once I was able to ejaculate in forty minutes, but that's just once.

I'm wondering if this is normal, what we can do to help her last longer and help her so she doesn't have to work on me for so long, and I'm wondering how this would affect us if we decide to have sex. I'm worried that during sex she'll orgasm quickly and that I will have to stop for fear of hurting her if I haven't orgasmed yet (cause most of the time once she orgasms she asks me to stop for a while before trying it again).

Alexi