Any insights?? Help!

I just stopped taking my BC pill about 2 weeks ago. I had my normal period from the 12th to the 17th. Today is my last fertile day according to glow. Yesterday I had light pink spotting and overnight, when I woke up it was brown. Now today it's very heavy, almost like another period, but I just got off my AF. What could this be? A sign of pregnancy? A side effect of coming off BC? Help!