I was there in my early 20's too. I didn't loose my virginity until 21 and then after that I just never really enjoyed it. I found myself doing the same things, crying silently, wanting it over......in my last serious relationship before my current one, I had the same feelings, not being attracted to him in bed etc.......evenutally, for me, I realized he was a good friend but I just wasn't into him romantically.
In my current relationship (I'm now 29 and have been with him for 10 months) I finally enjoy sex with him and its a fun and pleasurable experience, not the dread and gloom I experienced before.
I don't know if its the same for you, but I wanted to let you know that I was there too, that I understand.
Welcome to PC!
~Rayna