Music disappearing from Library every two or three days

[mad_surgeon]

Hi guys.
I download music cause I'm a premium user so it doesn't use my data from the mobile each time I want to play my music. I put it on my sd card and it works. But each time I restart the app it has disappeared from "my libraby" and when I go to the settings it has changed from "store your music in the sd card " to "store the music in your mobile phone".
Each time I have no more music in the storage and need to download it again and again. Don't get what's wrong in my app...
Note that I got few weeks ago a message from spotify that was saying that they deleted my whole music from the phone cause I downloaded from 3 different devices. I didn't but that's what they said ... maybe need to contact them and tell them to let me use spotify on my phone ?
Thx for helping me.