Can’t be pregnant right?

Okay we all know that you can only get pregnant around fertile window/ ovulation. And that ovulation always occurs 12-16 days before a period. My period is very regular and my ovulation day was 2 weeks ago. On a drunken black out night I may have had sex with someone, from my knowledge a condom was involved but I just don’t know if we had sex for real. This was about 3 days before my supposed period. Fast forward to the day I was supposed to get my period (yesterday) and it didn’t come, and still didn’t come today. So me being myself, I’m freaking out, but logically it’s just not possible right? I was also on antibiotics for 10 days which I finished on Sunday, so idk maybe this caused a delay. My period has been late before but it always freaks me out when it is