I'm confused

UPDATE 1: I took 3 tests and they all were negative. I'm going into day 15 of being late.

So AF is 5 days late. I can't remember if my fiance and I BD'd during my fertile window. I did just move in to a new place and there is another woman living here. She just had her period and I figured if mine was going to sync up with her's, it would have come a week early (it has every other time I've been around a lot of other women) is it possible that it could be coming 3 weeks late or should I get a pregnancy test? I'm trying not to get my hopes up, but my period is NEVER late. It's always on time or early. 😩