Could I be pregnant?

So Easter Sunday I was with one of my best guy friends. One thing led to another and we ended up having sex! I don’t remember much of it because we had both been drinking. All I know is he didn’t have a condom and I’m in the process of switching birth controls so I wasn’t on it this last month. He says (very detailed, sorry) that he “couldn’t stay hard” so we had sex for like 30 seconds. This may sound stupid, but I took a Plan B 2 1/2 days later, before the 72 hours. My period was due yesterday and it didn’t come. Are my chances of being pregnant very high? How long can Plan B delay my period?