If your girlfriend is comfortable discussing her fear of sex or her concerns about intercourse or other sex acts with her doctor I bet she’d get some good advice and reassurance. But if she’s not ready to talk to her physician about her fear of sex or her reluctance about it on her own, you can’t make her. Pressuring her isn’t going to work. It’s just going to make her more tense.
When you said that you don’t get to perform oral sex on her “the want you want to do it,” it seemed to me that you may be just moving too fast for her. It’s very normal for women to feel like certain sexual stimulation is “too intense.” That’s your signal to listen to her and reward her for communicating with you by slowing down and/or backing off. Stop expecting her to have more than one orgasm. She may not be able to, and she may feel that she’s not doing it right or that she’s disappointing you if you tell her that she can or should be having more than one.
It’s wonderful that the two of you are communicating about this. Keeping that channel open is the key to a good sex life. I think, though, that you’re really going to have to slow down a lot. She’s not experienced like you are, and she’s not just learning to navigate your body, but her own, as well. Men are a lot more goal oriented when it comes to sex. Women can get a lot of pleasure from the long warm up and slower, smaller gestures. If you can find pleasure in knowing that not every time you have intimacy it ends in an orgasm, then she may not feel pressured to perform and may feel less tense about sex. Sometimes it’s not men who are pressured to perform, but women.