AF Late, negative test HELP PLEASE!!!

Eymy
So as per Glow and Ovia (yes I use 2 different apps) Glow said I was suppose to get my AF yesterday, Ovia said I was suppose to get it Monday. So either way I am late. I've been having a horrible taste in my mouth (sorry if TMI) and I have been nauseated. But I took a pregnancy test today and it's negative. Has anyone else had a negative test but actually been pregnant?