Hello, I'm 15 and my period is only about 2 yrs old so I'm still getting used to all the symptoms. The calendar on this app tells me that I will get my period on April 21. However, I've been having a lot of period symptoms over the past few days, cramps, breast tenderness, mood swings, backache and tiredness. Will I be getting my period at the time of the calendar or sooner than that? Like can period symptoms occur without getting your period?