Does anyone with a long cycle 35-43 days, know when they ovulate?? Help

Mel_
Hi girls,
I would like answers from ladies with long cycles, 30-43, my one is usualy 42-43 due to PCOS, but have u seen a patern to where u ovulate?  What days? Opk tests not working for me, always negative, and applications are not always right. Please comment. Thanks