The app is not in your body to know what’s going on. It’s only a prediction that is bound to fail. Even with regular periods. Have you noticed days that your period comes later than the app predicts? In instances when ovulation is delayed maybe due to stress or illness, the app doesn’t know this. The days it predicts as fertile will actually be infertile days. And the days it predicts as infertile will turn out to be fertile days. You know what will happen when you make when you are fertile right?