Forgot a condom

My boyfriend and I decided to have sex in the car and forgot a condom. I'm not on birthcontrol but for some reason I thought we'd be okay anyway. Not realizing that I was on prime ovulation week. We tried sex for a few minutes but he was too worried about getting me pregnant. But what about pre cum? Does anyone have any advice? Should I just stay cool and hope for the best? Plan B? Anyone have any unfortunate stories where they did end up pregnant?