custom skins not working

Hello. I'm reporting a bug in the custom skins of Minecraft MCPE. Recently I have been downloading skins from online and sometimes they will work but a new problem has come. I was playing on a private server with a friend of mine and when she tried to change her skin my skin immediately became hers. Currently, I am unable to play Minecraft with my own skin. When I try to use my skin the skin becomes invalid and this has happened to all of my skins no matter how many times I download it. This is a very frustrating bug as I am only able to use the skins Minecraft gives to me, which are the Legacy skin pack, and the MineCon 2016 skin pack. I would not like to have to delete Minecraft and re-download it as I would not like to have my very valuable worlds deleted. Please help with this issue, I have asked everyone I know and none of which know how to fix it. -Bianca Ribeiro