Just curious

So I know this is personal but just need a little insight if possible! So I stared taking pre natal vitamins and fish oil ONLY for the sake of my personal health and my boyfriend and I I would say 3 days ago had unprotected sex. We never have before until then and also I felt somthing warm inside of me but he said he didn’t or doesn’t think he came. But it’s been two days since my period was supposed to start and nothing. No spotting or anything. Should I be concerned? Would it cling that fast although I was supposed to have my period a day after we did our thing? I don’ know I just need some help please! Thank you in advance!!