My period is now four days late, and I have been quite regular since I first got my period 5 years ago (I'm 16). My previous two were September 8th, lasting four days, and October 6th, which lasted 5. Me and my boyfriend had unprotected sex that could have only resulted in pre-cum entering me, which I know can sometimes contain sperm. I believe I would've ovulated somewhere around 3 or 4 days later (somewhere between the 21st and the 23rd of October), but now it's the 9th and I'm at least four days late. I took a digital First Response test today and it came out negative, much to my relief, but I still have a missing period. I have been very stressed about this since the 5th though, and I'm wondering if I could maybe be pregnant or if stress could possibly be causing my period to be delayed?