Precum can get a girl pregnant BUT it really does need to be in her vagina. On or near is unlikely to result in pregnancy. Sperm is smart but not so much so that it maps out exactly how to get to the egg if not directed. If you got sperm in her vagina, then possibly you could get her pregnant but overall, this doesn't sound like it would ever really happen in the real world. Buy some condoms though as you are dangerously close to unprotected sex with this activity. good luck