Late Ovulation with Clomid

I am wondering how many people have experienced late ovulation on a Clomid cycle. I am on my second round of 50 mg Clomid days 3-7 (didn’t respond to the first round). I am on day 25 and still haven’t had any positive OPKs. I had several days of creamy CM and very tender breasts last week and thought I was close to ovulating but still nothing. I’m wondering when to throw in the towel and give up on ovulating this round.