How to track with Mirena & no period

Hi guys! So I've had my Mirena for almost a year now, previously having a NuvaRing and BCP. I use it to prevent pregnancy and regulate my cycle, as I have PCOS.

My question is, how exactly should I go about trying to track my cycle and everything with Mirena? I don't get a period at all. All I get is a seemingly random cycle of slightly different discharge each day. Is there like a pro guide for identifying mucus? Should I just rely on temping (which I've never done)?

Thanks!