I seriously hate the clearblue advanced opk. This month I got positives on another type of test when I was having symptoms, but no positive from the clearblue. And previous months I've gotten false positives from the CB when I knew I couldn't be ovulating. In my opinion, the CB advanced is overpriced and doesn't work very well! I find the cheap wondfo's on amazon work the best for me. If you keep having problems, I would play around with some other brands and see what works best for you.