Bleeding while having sex

I am 19 yrs old and i have been with the same guy for almost 4 years. we have been sexual active for 2. While we were in the middle of having sex i noticed i was bleeding so i went to the bathroom. it was bright red not like my period and lasted like no more than 10 minutes. We decided to wait a while before having sex again. well about a wk and a half later we tried having sex again and right in the middle of it i notice i am bleeeding again. It was no different then the first time and i know its not my period because i am on the pill and im not due for another 2 wks. I was wondering if anyone has any idea what is wrong because its embarressing and a bit nerve racking and also i am in no pain what so ever..