EBF and Period ???

Carli • 30

So I'm almost 4 months postpartum. I've been pretty much exclusively breastfeeding. We usually give my son one bottle 4-6 oz of formula a day and the rest I breastfeed. My supply isn't quite where I want it to be but I've recently started taking fenugreek and its helping. I'm also on the mini pill.

I think I'm starting my period. I'm nauseous and crampy and have started bleeding.

I thought you really didn't get your period if you were breastfeeding and on the mini pill.

Can someone explain, please?