Anna - I had the BT's for the first month or two to establish that I had O'd, then they didn't worry after that. I was taking Clomid days 3-7 and at the start I still didn't O until Day 24, then it started getting quicker each month - to either CD 18 or 19. But the main sign for me was I had intense ovulation pain in my right ovary for the first time in my life, so I knew it was working. I was told that OPK's aren't accurate for people with PCOS, but I can't remember the reason why.