CD 37 and No AF. Venting and Worried.

Megan
Some background.
DH and I have been TTC for three months. 
My cycles are 29-30 days. My periods last about 4-5 days. This cycle however, has been different.
On Feb 20th (fertile period per Glow) I had brown spotting that lasted about a day and a half. I never have had ovulation spotting before, but rationally it is what I thought it could be. 
My period last month was also weird, it only lasted for three days. I then thought what I experienced feb 20th could of been implantation. 
I took a test yesterday and it was BFN
I am now on CD 37 and have had none of my coming period symptoms. The only thing I have is slight cramping. No AF yet. 
I am worried because if I am not pregnant, why is my period late? I don't expect any answers I am just worried.