What Causes Heavy Vaginal Bleeding After Intercourse?

My period started on Oct 25 and ended on about Oct 31. I had sex with my boyfriend on Nov 2 We didnt use a condom and he didnt pull out. A couple of days later i had heavy bleeding. First it was brown then it began to get heavy. Lasted five days. Im not sure if thats implantation bleeding or what? Am i pregnant?