Creating World then they dissapear

So I'll create a new world and play for a while and close the game, but when I log back in the worlds gone but not deleted because if I try to create a new world with the same name it will show up with: Survival (1) while ones with a new name will show up with: Building, I find this a problem and it seems to not be fixing its self. It happens with the new release and I never had this problem before. If this could be fixed I would forever be grateful.