Can I get pregnant if he came ON my vagina?

My boyfriend and I were having sex in the missionary position and he always pulls out. I guess he wasn't as quick as he thought because he ended up ejaculating on top of my vagina but it dripped down before I had the chance to clean up. The sex was very well.. lubricated so I don't think sperm would have a chance to get inside because I cleaned up but I'm wondering if it's a possibility?

EDIT: we are not using contraception because we are not trying and not preventing pregnancy. If I were to become pregnant we would be very happy, I just wanted to know the likelihood and if anyone else had conceived this way. Thank you.