I can't nut with my girlfriend
I hope you are joking. Why not?
She tells me that if I don't know how to do that then she can't help me
Maybe you'll just have to try a few different things. You should try communicating your likes and dislikes with her.
I still think its her fault. I don't know what else to do
You have to talk to each other if you want to work this out. You need to figure out what is going to work for you.