Pregnant or paranoid?🤔

About 2-3 weeks ago (during my fertile window) I had unprotected sex with my boyfriend & we've been talking about what if I'm pregnant.. 
I was due my period today & haven't gotten it & I've no cramps or any signs of my period coming. Am I just being paranoid or could I be pregnant? Can anybody tell me how many days after my due date for my period should I take a pregnancy test?🤔