spontaneous bleeding

hey everyone. I have a question maybe some of you can help.. I'm on birth control and my period isn't due til Thursday next week, but today I was getting dirty with my boyfriend and he stopped and said there was something wrong, and when we looked I was bleeding. red blood not brown spotting blood. do you guys have any suggestions as to what this might be? I'm gonna make a doctors appointment regardless but I'd like some peace of mind in the meantime... thanks .