My last period was 11/01/16 and ended 11/05/16 it was supposed to of started 12/01/16 took 4 pregnancy test 3 came back negative and one came back false...it didn't have anything show up...I have a doctor's appointment with the GYN Tomorrow to check things out. I have had a diet change...and I have been stressed and have had some bad mood swings...but I come from a past full of abuse and stress...and never once missed a period...I'm no where near as stressed as I ever have been on my past....what else could it be??