Sex question?.?.?.?.?.?

Me and my bf haven't ever had sex but we want to try oral sex next week and I really want him to come inside me and I asked him if he would stick the head of his penis inside my vagina a little bit and come inside me.. I am a virgin and I was wondering if it would be possible that I would get pregnant if he does this to me or would it not be possible because he did not put it all the way in?? Thanks :) btw we are both 18