No AF after miscarriage?

Gayle • Trying for seven years. Miscarried at 6 weeks on July 3, 2014, and again on October 14, 2016. Finally had my daughter with the help of the Ontario government.
I suffered a miscarriage on July 3rd. My hcg levels zeroed out by August 16th. It is now October 1st, and I have seen no sign of AF. Got a bfn when I tested this morning. I've messaged my doctor, but there's not much they can do. Any idea what's happening?