Calculating cycle with PCO

Caitlin • 💙🧒 Jun 17 💜👧 Jul 19 💛 Aug 21

We are TTC so I am wanting to calculate my cycle. I understand that it is about 12 to 18 days between ovulation and your period, is this the same with PCO / irregular periods? It has been more than 3 weeks since ovulation but pregnancy tests are all coming back negative... Starting to freak out!