Been TTC for 8 months and using OPK for 5 months or so. With the Boots colour test ones I have had the line go darker than the test line which I assume is positive but this has only happen maybe twice. I have also used the digital tests and never had a "yes"! I am 99% sure I am ovulating as I have all the other signs plus had two transvaginal scans (in separate months) which confirmed I had ovulated a few days before. Have tried doing the tests at different times of the day but never seem to get a "yes". What am I doing wrong?