I just recently started taking birth control and it has

Patient: I just recently started taking birth control and it has been about 3 weeks and i am just starting my last week. I know that the 4 week is when my period is supposed to come on but it haven’t and my period tracker say i am 3 days late from today. Last time i was sexually active was on may 16, 2015. Me and my partner started off using a condom but then my partner took it off and we continue to have sex. My biggest question is can i get pregnant from the pre-ejaculation? I did see that he actually ejaculated the sperm but it wasn’t inside of me it was on his chest. So we are having a bit of a scared moment and not sure what to believe.

Doctor: