The past 3 months I've had very sore breasts about 2 weeks before my period started. According to my period tracker, I am now 21 days late. (Last period was July 29th, its now Sept. 23rd) My breasts are not tender, but I have been getting headaches almost daily and I am very fatigued. The past two days I have had a brownish spotting that's only noticeable when I wipe. I took a hpt 4 days ago and it was negative. What's the likelihood that I'm pregnant?

You could be. Schedule a blood test with your doctor.