It sounds like you might of started your period, during intercourse or You just broke your hymen, don't be to worried just go to the doctors, you'll be fine, good luck!
Well unusual but you could have broken your hymen. If you've been having sex this should have already happened but sometimes for whatever reason it does not always break the first time. Or another thing is that you could have conveiniently started your period during intercourse. In my opinion talk to your mom about this since it appears you can communicate with her in regards to your sex life and if it continues go get checked by a gynocologist. Best of Luck BB
IN MY OPINION IT SOUNDS LIKE YOU HAVE BROKEN YOUR HYMEN, I KNOW IT SOUNDS ODD BUT IF IT HASNT BROKEN BEFORE THIS INCCIDENT THEN IT IS POSSIBLE. I SAY THIS FROM KNOWING SOMEONE PERSONALLY WHO HAD BEEN HAVING SEX FOR YEARS AND HER RECENT BOYFRIEND JUST BROKE IT, SHOCKING BUT TRUE.