I think I may be paranoid..

Im 18 and my boyfriend(20) and I have been together for over a year. We have started having sex for a few months now. He wears a condom and he pulls out( is not in me when he cums in the condom) the 13th was the last day we had sex and he knew I was gonna be starting the next day. But it’s now the 15th and I haven’t started my period yet. I’m starting to get paranoid about all of it. I haven’t missed a period in a while. Which was a few years ago and was 2 weeks late but I was a virgin so I knew for a fact. But I also think it could be of stress. Since I had prom the 13th and some family issues on top of that all weekend. I don’t wanna tell him till a few more days go by because I don’t want to stress him out either and have him worry about it. I know y’all can’t give me medical advice but your opinions are definitely appreciated.