[rcoreyus]

On re-reading, I noticed something: you get a guilt trip if you suggest doggy style? Why? What reason does she give? My first thought would be that she is completely sexually repressed, but she does let you give her oral so that can't be it. Is she maybe just so selfish that she wants you to do all the work and doesn't care what you like?

[dyunysus]

I have to agree with rcoreyus. Speaking from experience, i am married to a wonderful women. However she was sexually abused at a young age and trust was a huge issue in the beginning of our relationship (maybe your girlfriend was too?). She always want to stay on the bottom so she could see exactly what i was doing. As far as her not wanting doggy style, she probably had a lover before who tried to sneak in the back door if you know what i mean, so she maybe scared to be in that compromised position again. If you want her to get more involved than just laying there, make sure there is plenty of foreplay, use your fingers to bring her to orgasm first, then oral till orgasm, at that point she should be pretty much throwing you down and riding you like crazy.
Good luck and be safe!