Late :/

Alright I'm kind of worried. My period is late by 2 days (I know it's not a lot but I get worried easily). My boyfriend and I had sex a few days ago and he went in without a condom (for about 10 seconds, didn't cum, and I'm not on bc). Is it possible that i'm pregnant or is it just stress because of school? I'm always worried that precum can get me pregnant. Am I just freaking myself out?