What Causes Bleeding And Lower Abdominal Pain?

Well I have been having problems wirh my stomach,like in my lower part of my stomach,but I seen to not kno what is its a sharp pain then it moves to my back,also me &my boyfriend just recently had sexually intercourse one night then     that morning we had sex again I have a question why would I be bleeding and im not suppose to come on my cycke until the middle of the month we did this on the first I was alil worried cause I havent stop bleefing in my stomach hurts in the lower part and idk what to do so if you can help me that would be nice!!!by the way my name is Ryan&im a GIRL