So, i had sex 6 days ago, im not on any form of birth control, but we did use a condom, although when i was on top, it slipped off, were pretty sure it had only just came of when we found out it came off and we stopped straight away, he did not ejaculate, but it was his first time, so chances are he did pre-ejaculate. I didnt take morning after pill as i thought it wouldnt be possible, because the condom was probably not off the last time he went inside me, it may have been about half way up his penis or something.. what are the chances of pregnancy occuring from this??

My last period was 13 days before this happened

is there any chance of this at all?