Mini Pill Effectiveness

Staci
Hi,
I'm currently on my second pack of mini-pills. I usually take it at 10pm, but tonight I took it at 10:30. My bf and I had sex around 7:30-8pm and while he usually pulls out, tonight he did not. Now I'm panicking that I'm going to get pregnant, and I absolutely CANNOT let that happen. Should I go to the drugstore for Plan B or am I overreacting? Please help!