I'm on tri sprintec birth control and I have been on it for about 8 months. I've been on tri sprintec for 8 months, I haven't missed a day but I haven't taken it around the same time during the day. Me and my boyfriend have unprotected sex but he doesn't finish inside of me, he pulls out beforehand. My question is if I had sex before a took a pill one day, could I be pregnant, I usually get my period today, but haven't? Help!