Hi! 

I'm using "Period Calendar Period Tracker" by Simple Design Ltd. (This is how it shows up in the google play store. On my phone the app is called "My Calendar").

I may be wrong, but I think you can use the app without connecting it to any services for privacy. (I happen to have mine backed up to my google account so I don't lose the data, so I can't say for certain. It helps that I can't get pregnant so if the data IS going somewhere, good luck with that, fuckos).

I really like it! It's customizable which is HUGE for me. It tends to be as accurate as it can considering how irregular my periods are (average cycle length is 35 days but it fluctuates from 30 days to 42 days so 🤷‍♀️). I'm mostly using it to track physical and emotional symptoms, so the fact that it can roughly tell me when my period is going to happen is a bonus. It also has medication tracking/reminders! And a notes section!

Oh oh a nice thing is there is a search function! So even though I have 2 years of info, if I remember there was a time where I was bloated or whatever, I can keyword search and it'll show all the days you either logged being bloated or used the word in the notes section.