What are the statistics of a woman getting pregnant when a man d near/on her ?

Sorry I didn't mean to be so blunt with the v word. I'm just wondering what the statistics were since I know it is possible. My boyfriend and I messed around tonight and he d pretty much on/against my business, no underwear on either of us. A bit worried..I'm going to take a plan b pill just to be safe, but in the meanwhile I'd really like to know the statistic.