Strange Test Results or Just late?

Jessika
Hi! I am just looking to see if anyone can relate to my story! 
So here it is: a few days after ovulation I felt a bit of cramping, very sensitive nipples and tiredness. Then a few days before my period was due- no real symptoms. 
I have a 28 day cycle and I am pretty regular. I think the long I went was 29 days.  According to my calculation I should I have my period on Monday but according to Glow and my doctor I should get my period today.
For the past 2 days I have had very bad cramps, high temperature/hot flashes and short of breath. 
I took a pregnancy test on Sunday and it was negative (but it wasn't the first morning urine) and another one just now at the doctor office and still negative.
So am I just very late for the first time ever, mentally blocking my period or something is up with my body? 
What do you all think?