Need help - brown spotting

Jessica
I'm 16 dpo and AF was supposed to come on Saturday. 
Since Friday I have had some cramping and feelings of wetness and bloating (like I usually do right before AF), however she has not arrived.
​I have only had a little spotting (mainly brown) and when I checked my CM it was like thicker and brown? I had take a pregnancy test a few days ago and it was BFN. When should I re-test? Only other detail is that this is my 1st full cycle off nuvaring, before which I was always very regular. Any ideas?