What Causes Thick Bleeding And Cramping After Intercourse?

I had unprotected sex with my boyfriend twice, but he never came. it was all pre cum and it was never longer than ten minutes both times.This was about a week ago. Yesterday we tried having sex and i began bleeding. Now i have cramps, and i keep bleeding this chunky brown stuff and it wont stop. It didnt hurt when he inserted himself, do you know what this could be?