Worried about my menstrual cycle.

Maiya

Well i have been using this app to help me with when i was suppose to start my period and the first date it said was the 2nd and it hasnt started. When your period hasnt started you keep clicking it hasnt when the next prediction day comes and here i am October 7 it still hasnt started. I havent had unprotected sex what are some things that will help my period come.? and can someone tell me why my period possibly hasnt started yet ?