My period comes right on the expected period date on this calendar. It is every 28 days, but my calendar now shows 36 days. Is there a reason the calendar made a change?! I have been using the app for about a year. It is weird because I'm on day 31 and still haven't gotten my period. Can the calendar be wrong and I'm pregnant? Or is the calendar correct? Why did it change out of nowhere? Confused!!