After was due the 23rd but it seems to be early!?

Hey loves, every month my period comes about 2 days earlier than glow says. I even calculate things on my own, but the past 4 months it has come early by 2 days. I got excited this month because, I had one dot of brown cm at 9 dpo, but then today at 10dpo, it's my af! I don't know if any of you ladies have this problem. But glow will say one day and then my af comes early! I feel like it is throwing my cycle of every month and I get confused as to when I'm actually ovulating. I know you can't go by this app 100% but it's frustrating! :) thanks for any help! Xx