Opk test not + anymore

Victoria • TTC#1 RAINBOW BABY=) miscarriage around 6weeks June 2015. Struggled with ovarian cancer at age 17 only have one full left ovary and a small portion of my right ovary.
So yesterday and the day before they were full blown ++++ now I just tested again today but it's not like it was yesterday so how long after the surge drops should I ovulate we've been having intercourse the past few days and will again tonight so I think we're good just want an estimate of when I should ovulate. Picture below is the one I just took.