Implantation or ovulation?

Jasey • Married October 2014 and Pregnant with #1 due October 2015!
I am currently on cycle day 20. The night of December 1st I noticed some light spotting when I woke up the next day it was gone. This morning (December 3rd) my cm was brown. Glow says my period is due in 6 days but sometimes I don't get AF until about 4-5 days later than it says I will. I have also been doing opks and they're all almost positive.