Ladies with irregular cycles!!

So I have an appointment for a checkup tomorrow with my new OBGYN. I also happen to be 20 days late for my AF, I’m on cycle day 53 currently. My cycles have always been somewhat irregular, fluctuating a week or so every couple of cycles. I think I might have PCOS, but my previous doctor never did any testing to find out why my cycles are so irregular, she basically just shrugged it off. Which I didn’t worry about until recently because now that weve been TTC for 9 months with no luck, I’m worried. I plan on asking my new doctor tomorrow about it, but basically what I’m wondering is what kind of testing your doctors did to find out why you’re having irregular periods/ or if you have PCOS? Any input is appreciated, I just want an idea of what should be happening at my appointments to find out what’s going on with my cycles. Thanks!