Irregular cycles TTC 2 years

Tory • TTC #1 for 2 years with PCOS
I have very irregular periods, I don't even know when I'm going to get them. Last year I had them for 3 weeks in feb-March and also 2 weeks in October. 
I also had them for 1 week this year Late march. 
My question is how do I even know when I'm ovulating? I don't wanna miss an opportunity when it may only come twice a year, I also have PCOS. It's so frustrating and stressful. Has anyone else had or have the same problem as me?