post coital bleeding

my boyfriend and i had sex the other night and afterwards i noticed i had been bleeding. i'm guessing i started bleeding while we were having sex. this has never happened to me before and i've been having sex for almost 4 years now. this freaked both of us out and i am going to see a gyno tomorrow, but then my boyfriend told me that he washed his sheets and stuff last weekend and he noticed there was blood on them so we wondered if it had happened the last time we had sex before the other night. i'm really curious as to what the deal is. ive been reading a lot about some of the different things but i didnt know if tehre was another answer or not. i had my period for about 2 weeks..which is abnormal too..i had it for a week then we had sex and then i still had it for another couple days and we had sex again. i know the blood though was not from me menstruating...it was actual blood.