Period/pcos question

I was on a progesterone only birth control for a few months, when I started it I was on day one of my period and it stopped it completely and I didn’t have my period for months (I have regular just extremely heavy and painful periods) and even after I got off of birth control I still didn’t get my period for months. I finally got it after I started the same birth control again but I’ve had my period 3 times in the last month and it’s heavy. I don’t know what is causing this or if it’s just the pcos? I’ve been regularly taking my birth control for about two months