13 DPO - Brown spotting

Woke up this morning expecting to see AF... but nothing.  Nothing at all.  Took another IC HPT with FMU, negative, white as can be.  All day today I have been going pee about every 30-60 mins.  Not usual for me when at work. Around 10am, I noticed some light brown CM, not even that I needed a pad or pantiliner for, just when I wiped.  Had that a few times throughout the day, only a tiny bit each time.  After work I POAS, an OPK, and the test line was darker than yesterdays.  Not as dark as the control like, maybe half way there.  AF due in 2/3 days unless she is slowly hear now.  Still having cramps only on my left side.  I just wanna know already :(