I Was A Virgin Up Until Last Month. Me And

i was a virgin up until last month. me and my partner tried to have sex but am almost sure he didnt put it in when he climaxed. this happneded on dec 3rd. but he was a little doubtful. but i still took a pil to be on the safe side. my last period was on nov 24th. next was supposed to be on dec 25th. but the lady at the drug store said it will be a week late because of the pill. and now its the 5th. is it common for it to be this late?