Brown cm but BFN? Am i out?

Emma
On saturday at 12 dpo i had some cramping and a little light pink spot, today i'm 15 dpo & due for AF i tested this morning & got a bfn but when i just went too the bathroom i have a little brown cm but no cramps & my typical period is horrid cramps. Could this be pregnancy sign & how long should i wait too test since this mornings was negative?