Today is CD 12, and my tracking app predicts I will ovulate around day 14 (Tuesday). I've been doing OPKs for three days now, twice a day, and yesterday's OPKs were darker than today's, although they weren't blazing positivies. I'm using up some internet cheapies but they're usually quite reliable and show a strong, dark line on the day of/day before ovulation. Am I doing something wrong?