Positive OPK on CD 39??

Kate • Kate & Kate Married AF 👰🏼👰🏻 Baby #1 on the way!

I'm SO confused. We've been TTC for 7 months with a known donor and never 100% sure that I've been ovulating each time we've tried. However, all signs suggest I ovulate around CD 20-ish? Today I got a very clear positive OPK with some pain in my ovaries. Also quite a bit of EWCM. Is this a very late ovulation? Is it caused by period? Early pregnancy? This whole TTC process has been incredibly confusing. TIA!