Pre-*** on surface of vagina. What are the chances of me getting pregnant?

My boyfriend and I fool around. We refuse to have actual sex because I'm not on birth control yet. He was rubbing his penis on my vagina, and the tip of the head went in like 2 or 3 centimeters. He jizzed shortly afterwards but always pulls away from my body completely. I'm worried that some pre-*** got inside of me, and I'm worried that I'm pregnant. I know pre-*** doesn't naturally have sperm in it, only if it picks it up from a previous ejaculation without a urination in between, but I'm still concerned. My mom and I already plan on getting birth control for me soon, so please don't lecture me about being ignorant about protected sex. My boyfriend and I are both terrified and we won't have another scare if we can help it. It's been about two weeks since the accident, and a few days ago I got my ovulation cramps, which is about exactly 2 weeks after my period ended. I have two weeks left until my period is due. I'm just hoping for some comforting advice on this. Let me know!