What Causes Vaginal Bleeding Post Intercourse?

i just had intercourse and i went to pee afterwards to clean everything out. i had a bowel movement and when i got up from the toilet i also saw this tiny bloody clump floating in the toilet. no blood came off of it and i don't know if it was vaginal or rectal. i didn't feel it come out, it was just kind of there. we didn't use a condom because i am on birth control and we had sex a while before that too. could it be semen from last time that just didn't come out until now?