he didn't finish inside me, but my period is a few days late

hello.

so me and this guy have been having sex for a few months now (only once or twice a month though) so in february and march my periods started on the 8th and ended on the 13th (probably because same days and stuff etc) anyway me and this guy had unprotected sex march 24th. Me and the guy started to have sex, he was in me about a minute. he then got a phone call tat said he had to go. So he took his penis out of me and then sat there for like 2 minutes jacking off ttying to come. he finally did and then left. My period app says that my period was supposed to begin april 6th, which it didnt. I have been so stressed with school and now this missed period thing. i have been freaking out about pregnancy and crying alot and it just sucks. is there a possibility im pregnent? is there a posiility that im just overly stressed and thats delaying it? He no way came in me at all. Thank you.