AF due tomorrow

April • 25 years old. TTC #1
On 7/3/16 I had dark brown CM when I wiped which later in the day turned into light pink. It never got heavier or turned into anything. I took HPT 7/8/16 which was a BFN. I am so confused I've never had spotting like that usually when AF comes she just comes but I feel like if was pregnant I should have got a positive yesterday although I didn't use FMU. I'm waiting for tomorrow to test again if she doesn't show. Has this happened to anyone else and got a positive test at a later date after testing negative? Please any info will help ease my mind.