She Can't Feel Anything During Sex?

My girl friend basaclly told me that out of the 6 months we have been haveing sex, it's either good or bad, never "amazing" as she says it's supposed to be ( her friend told her every time should be amazing, we were both virgins, and 18 at the moment. ) but she says that when its " good " she only feels pleasure on the outer side of her vagina, and when it's bad or slightly okay, she feels little to no pleasure. I try to angle her g spot or do the angling right. But no luck really, latley I've been struggling with lasting long but it's getting better. And also I don't know how she can't feel anything since I'm 6" long and 5.5" girth. Any advice?? PLAESE help

 

Sounds like she is used to masturbating and stuck on certain stimulation.