My girlfriend is not feeling it...

My girlfriend of 3 years is finally bored of our sex life it seems. She has never had an organism, although she says things like, 'But it still feels good' in order to cover up her disappointment and so not to hurt my feelings. It is not that I have been completely insensitive to her needs---she doesn't get into it when I try to give her oral, for almost a year she 'faked' organisms and never voiced what she really felt. Although I had heard that most women 'fake', I believed that she was experience some sort of pleasure.

Almost everytime we have sex, I feel pressure to perform up to par, but the same thing happens everytime---I will stop during sex in order to not orgasm (maybe for 5-10secs, then begin again) so that I last from anywhere of 20-40 minutes. Eventually I can no longer hold back--I experience a heightened orgasm from this, but this is short lived given that my partner has still not experienced something of that level.

What I am doing wrong? I realize everyone has specific needs. We have talked about what she wants or likes done to her. Yet these things have not really helped the situation. I feel guilty that sex is a more pleasurable experience for me.

Now here is a big part of the problem. We broke up for 5 months because a long distance relationship was not going to work (I moved out of state for this time). She had sex with another guy. It was a very pleasurable experience for her. I had tried to talk to her about it, but I ended up getting upset from feelings of jealousy and inadequacy, and she ofcourse was uncomfortable with the topic. Bad move on my part. It is not as sore of a subject for me now, but she doesn't like to talk about it. I have thoughts like "what did he do that I did not". The whole sex thing has put stress on all areas of our relationship. I think about it alot and want to talk about it, she doesn't want to.

We now have sex less often, and are currently 'taking a break' from doing anything physical. She has told me that she does not get excited about sex and cannot passionately participate. I am an attractive young guy, I'm athletic, I'm intelligent, I have a sense of humor, I have all these attractive qualities that mean very little when I want to make love to my woman.

Any advice or similar experiences?