Ovulating at end of cycle?!

Okay so quick background. Started tracking periods two years ago, after coming off the pill.

Irregular periods. Five years ago diagnosed with possible PCOS .

This cycle I decided to use the Clearblue digital fertility checker to see when I was ovulating. I started using it late (day 22) and it said low fertility which I thought meant I may have ready ovulated.

Next thing I know I'm getting high fertility readings!

Today - day 30 - I test and I get "peak fertility"! But from what I can tell from symptoms (spotting/CM) I think I'm having my period!

So confused right now. Is it possible to test high for Lutenisimg Hormone just before menstruation? Any else has experience of this?

:O