No AF exactly 2 weeks past ovulation?

I confirmed ovulation with opk, was on 7/15. But AF has not shown today and I don’t have the same CM I normally would have if it were going to happen today. I thought it was always guaranteed 2 weeks to the day after ovulation, but is that not the case? I’ve taken a First Response rapid result and it was negative. Just need to know if I should accept that for what it is or hold out hope another couple days?