I need help.

I'm not sure if glow even works correctly. Its making me upset because for the past 4 months I have started on the 15th or 16th and went until the 20th and last month I started early and this month it said I was suppose to start on the the 9th and now today I am 5 days late. This is messing with my head obviously and I just don't understand. Is glow normally correct when it come to that?