A TINNY BIT OF BLOOD AFTER UAL ?????? WHAT IS THIS?????? I'VE FINISHED MY BIRTH CONTROL PILLS?

YESTERDAY I FINISHED MY BIRTH CONTROL PILLS(THE LAST PILL WAS A BEIGE PILL NOT THE WHITE SUGAR PILL) AND SO NO LONGER ON PILLS. I HAD A VERY LIGHT PERIOD LAST WEEK AS IT WAS MY SUGAR PILL WEEK AND MY PERIOD FINISHED ON FRIDAY/SATURDAY. TODAY I HAD UNPROTECTED , JUST ONCE. BUT THERE WAS LITTLE LITTLE BIT OF BLOOD BUT IT WAS BLOOD. I AM UALLY ACTIVE AND ALWAYS HAVING UNPROTECTED . WHAT IS WRONG WITH ME??????