Late Period

Okay so I had unprotected sex on the 12 and my period was due on the 21. I have a regular period and the tracker has always been spot on. I've taken 2 hpt and both came out negative. I took one the day before my missed period and when it was 1 day late. Ive had my normal pms symptoms but I've been a little more nauseous than normal. Could AF just be late or????