Not being accurate

This is my first problem with glow and I've had this app for two years and I love it. Just recently this happened. I get a notification that my period is supposed to start in one day (tomorrow). Then it says my period starts in three days. When I go to the calendar it says that my period is supposed to start on the 17th even though these past 3+ months it's been around the same time. I'm actually surprised by this because glow is very accurate when it predicts my periods. It's also not letting me access pictures I just recently took.