me and my girlfriend used to have a close relationship and were comfortable with doing things, and now i'm left with a sexual desire that i won't get from her, and it aches when it comes to rejection each time. is there something wrong with me?

I wouldn't say something is wrong with you. Your feelings are normal but your actions are not.

Your desires are pretty normal. But you need to be aware of human design and system. Women's feelings and desires are massively stronger than men. But there are a bit of pattern to understand.

The first mistake: You are measuring the affection of the relationship by this content. That is a very invalid measurement. Unless this is what you looking for in a relationship. Then you must look for someone that look for the same thing.

The more you push, the more she rejects. Your pushy behavior can ruin your relationship. Or she'll accept doing it but she'll hate it and what's the worth if someone is not there by heart and will. And when a woman hates it, everything else about is useless and meaningless.

Woman needs to decide her feelings. They must be prepared for it physically and psychologically. They must feel wanted. Sometimes they need extra space. Sometimes they need time.

It's too difficult to guess a reason behind her current feelings and distance of such content. Because it could be anything. And as a man, this is your responsibility to figure this out and solve it. Pushing her constantly won't make anything better but only worst. Your path to understanding the matter is to be all ears and eyes. Communicate and be gentle.

It could be anything and many of them could be your own fault. But also  it could be anything such as a temporarily psychological deal that what she needs from you is mutual understanding and support instead of acting like a hungry man for one thing.