Yallllll so my foster child and I are basically on the same period cycle.. either I start a couple…

Yallllll so my foster child and I are basically on the same period cycle.. either I start a couple days before or she starts right before me (she is on birth control) she starts her new pack tomorrow and my period has yet to come!!!! I had my tubes clamped last April and have gotten a period every month. Ummmmmm what could this be. I have PCOS but like I said my period has been regular since I took out the Mirena when we tried for my daughter.