Minecraft app glitch. Skins/mods. Saving data.

Recently I have had to delete the app twice due to the fact that
The mod I wanted to use for my realms would not load at all. It would not let
me use the word I had used for the realm and when I downloaded the app
again it would not save any additional servers or outside skins, I have to continually
add my skin back and the other servers I'm on when I load the app.
I cannot add any outside mods, all that come from good sites that
I have been able to before. I am really confused as all needed
apps are up to date, any help would be great.