AF 2 days late!

So I stopped birth control June 27th 2018. Had a normal 3 day period July 4th. Accroding to glow I was supposed to start my period yesterday and i still haven't. I had some bad nausea and mood swings and tender breast last week so i took an hpt and got a BFN. This week all Im having is headaches and my boobs are still tender but no signs of AF. I took another hpt yesterday and it was also a BFN. Im wondering if this is normal after coming off birth control or could i possibly be pregnant.