Bleeding after sex?

My boyfriend and I just started having sex a couple weeks ago and have done so many times since then (he is my first). It hasn't been painful until tonight, it hurt really bad I could barely stand it and when he was done we realized I was bleeding a lot.... All over the bed and even still bleeding when I got home. He wasn't going very rough or anything. Is this something I should be concerned about? Does this happen to anyone else?