Ovulating AFTER CD24?

CD24 & I still haven't ovulated. Clomid 50mg on CD 5 to 9. OPKs tell me I geared up a couple of times but nothing confirmed by bbt. My last cycle was 28 days exactly, O'd on CD16 or so, but I'm anticipating having to take Provera to induce AF this cycle (I've only had one natural period this year), and I'm not sure when I should write this month off as too late to ovulate & just start taking the Provera.

At what CD would you say waiting for ovulation is a lost cause?