Question about OPKs...

Katie
I'm not trying to get prego first off. I am trying to prevent it/see if I'm ovulating. I've got PCOS or so they think. No actual cysts have been found... I used clomid to get pregnant last time and got a positive OPK on day 17. I was using the digital smiley face ones then. My question is... When I use the cheapie OPKs (from Amazon) I'm only getting a control line. A test line isn't even present, at all. Shouldn't there be something there?!?? I'm on day 15 right now. I'm going to continue to see but just wondering if anyone has experienced this same thing? I'm just wondering when we are ready to try if I'm going to need clomid again or if I can catch my own ovulation. Thanks!