Late period help.

Tiffany • Christian. Mother of 3. 3 living and 1 angel. 8 years together married 5.
I was suppose to start my period in the 12th of November (6 days ago).
I still don't have it and tomorrow will be a week late.
I took 2 digital test. One at 1 day late and another at 3 days late. Both said not pregnant.
I figured it was late and would come soon.
Still nothing at almost a week later.
So on Monday the 17th I went and took a medical grade urine test.
We thought we saw a very light pink line, but they said was not enough to say if I am pregnant or not. They suggest to come back in a week and retest. 
I have 2 kids both test came up positive for me at 2 weeks and 1 day late.
No new stress, more stress, or anything.
I have had light cramping on and off, more tired, and on and off feeling like I'm going to throw up. 
Not sure if I'm pregnant or why I'm late???