sprintec and bleeding during intercourse.

Remmie
The last time I was intimate was August 24th. I've had a period since then and had intercourse with a new partner tonight and began bleeding. I was not on birth control when I was intimate on 8/24. I started sprintec Labor Day weekend and I started a new pack of pills a week ago. Any ideas on why I started bleeding tonight? Has it been too long? Is it the birth control? He was very gentle with me.