This is my first month of using OPK's and trying to track my cycle (not doing temps though) so it's all a bit new. I've been testing since CD8 and am now on CD17, I got faint lines on CD 14, 15 and 16 but today it's completely blank. I know faint lines are meant to be negatives but any chance they can be positives for some people? In theory I still have time to O as I have 30ish day cycles and my cm is still watery/egg white and cervix highish and I think open. I'm of course now worrying that I'm not ovulating and am broken!