Hi

So I basically always remember my period being very regular 27 - 29 days or maybe 31 every few months. For maybe the last 6 months or so I've noticed it's started coming quite early. I write it on a calendar and use an app to track it, so here are the last cycle lengths for the past year based on the app. I have noticed the app sometimes seems to count the cycle length a day shorter than I do on my calendar for some reason

2019 - 26,24,27,27,25,26,25,26,27,25,25,24,28
2020 - 23,24,27,26,29,22

The 25 - 26 days don't bother me, but a couple of times it's gone earlier than that and I'm getting some health anxiety over it. Any advice appreciated!

I'm 25 years old of that's any help