System keeps changing my password

Since late May, I keep getting notices that my password needs to be reset for “security purposes”. At the same time, I get an email that my password “is all set”, as if I had done it myself. I HAVE NOT CHANGED PASSWORDS!! Your system keeps doing it by itself! It is very frustrating to have to change PWs on multiple devices every few days. I want to know why this is happening, or better, how to stop it from happening. Your phone “help” is worthless for anything other than the simplest problems, which this is not.