What Causes Prolonged Vaginal Bleeding After Having Sex?

yes. well i had sex with my boyfriend for the first time three days ago. it was all unprotected sex, right when we were finished i saw blood stains everywhere. now its three days after having my first time sex and im still bleeding, everytime i go to the bathroom it stings a little to pee, i dont know if its something i should really be concerned about. or if i may be pregnant