Hi, I'm new, just signed on here. for 2 of the 3 months I've been TTC, all my OPK's were negative. I did the tests 2/day, once at 2 and once at about 10pm. Started on day 11 until day 17. Regular 29 day cycle. This month though, I started BBT, and it showed a clear thermal shift. I DID O according to the chart on CD 15. I trust that more than the OPK. MAybe I didn't hold urine for long enough. Some lines were nil and some were half as dark as the control.