Broken log-in

This is stupid. Im playing Pokemon go one day and then it logs me out, it was no big deal at first, then when I try to log back in with my exact username and password, it says: Unable to authenticate, please try again. And it does it every time in the past 3 months. Im getting tired of it. I even deleted and re-download the game and it still doesnt work. Please fix this.
(I cant let my dad beat me to a legendary)

Ericx77 about Pokémon GO, v1.39.0