According to glow I'm not ovulating lol?

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 this app is Great other then the fact it's COMPLETELY off when it comes to me ovulating I just start the app but it's way off because according to glow I have a 3% chance of conceiving yet I took ovulation tests yesterday and today and they are 100% positive so I should be ovulating soon. Why is the app so far off???