All minecraft mcpe worlds have been deleted

Well, all of my Minecraft worlds suddenly disappeared. I simply went on to the game, it took slightly longer to load and when I actually got on none of my worlds were there. I had still my friends but my worlds, servers and skins have been deleted. I tried everything, but nothing worked. Yesterday I tried just starting new. So I got to work making a new world but when I went on today my world had not been deleted however the data on it had.