Is it Plan B or pregnancy? Opinions greatly appreciated!

I had unprotected sex with my boyfriend about two weeks ago (yes, I know, a mistake on our part). He did not ejaculate inside me and had not ejaculated prior to having sex for about a week. Even though I'm fairly certain there was no sperm in his pre-cum, I still went out and used Plan B within my 72 hour window. I was due for my period 3 days ago and have not gotten it yet. However, yesterday I had cramps throughout the day - something that usually occurs a day or two before I actually do get my period. I’ve even had some today. My question is, could Plan B delay my period or might I be late because I’m pregnant? I really hope it’s the former, but I know there’s always a chance of pregnancy. Obviously if I don't get my period for another few days I'll take a test, but I'd like some opinions for now. Thank you.