I got my period back with my son at 8 weeks PP. He was nursing every 2 hours, even at night and we did not supplement at all. I was so ticked off. My friend who started supplementing at 6 weeks, whose daughter slept through the night from almost the getgo, her period didn't come back until she stopped nursing at around 10 months. I was not a happy camper.
I expect my period to rear its ugly head any day now. Teagan goes 3 to 4 hours between nursing during the day, will cluster feed at night, but will only wake up once a night to nurse.
So it can come back early