Ovulation Time

I have PCOS and I have been trying to get pregnant for a year. For my last few cycles I have been taking Femara. I am trying everything that I can think of to figure out when I ovulate. I have an Ovusense monitor that I use and I take ovulation test. I am currently on cycle day 19 and according to the calendar and my Ovusense I have not ovulated yet but according to the OPKs I have been doing it looks like I may have ovulated already. Can anyone give me some advice on this?