Spotting - Am I Out?

I really thought I was pregnant this month. My boobs have been killing me, I've had to pee a lot, and I have had some terrible headaches. For the past 3-ish days, however, I have noticed some light brown/tan spotting - but I only see it when I check my CM or CP.  It's not on my underwear or when I wipe. I have been getting a bit crampy, so I am just assuming AF is on her way bc she's due tomorrow. So, is this just the start of AF or has anyone that got their BFP noticed light spotting for a few days?