I agree with a lot of what people said above.
You mentioned that she doesn't perform oral sex on you and that you said something to the effect of "well you did it to your ex".
That is the wrong way to bring it up. It's very insensitive and really doesn't show empathy. Most likely, her ex was very abusive with oral and she is so turned off by that experience.
(It makes me cringe that men abuse women like that)(I am a man btw)
A better way to bring it up would be along the lines of "I really enjoy oral sex and fantasize about you giving it to me, I would like to have you try it and setup some rules/boundaries that we can be comfortable with."
An example of such boundaries could be:
- No thrusting into her
- No hands on her head or hair
- No applying pressure
If she does agree and start doing it (but it sounds like there are several other issues at play here), be very supportive and complementing while she's doing it and after:
- "Wow you did a great job"
- "That feels so good"
This will help boost her feelings about it.
However, I must warn you that she might lash out at you or get upset. Simply stop having oral, tell her its OK and ask if each of you could put your clothes back on and simply lay down/relax together.