What Causes Heavy Bleeding After Intercourse?

Hi. I have a question. So I had sex with this guy for my first time ever, and after a couple minutes i couldn t stop bleeding. When I would stand, blood came gushing out non stop. I was getting blood clots the size of my fist coming out of me. I passed out twice and had to get a blood transfusion. I am currently on birth control to regulate my periods, but I m not sure if I should continue having sex after this happened. SOS!!