I've never tried using OPKs before but I decided to try pretty late into my cycle this time. On CD 14 I took two tests both very faint but had obvious visible pink lines (which from reading the instruction I know to mean that the tests were negative). Then this morning CD15 I took another OPK and now there is no line at all. Does that mean I could have ovulated on CD12 or 13? Or that ovulation is on its way? My other (probably dumb) question is that, given that hormones don't just leave your body quickly, would an OPK still have a faint line the day after ovulation? Thank you in advance