Worlds still reset

Minecraft Worlds still keep resetting, Ive checked my storage room and made sure that I wasn’t using any other program other than Minecraft but it still keeps saying “There was a problem loading this world” and once I clicked ok it put me back to thhe world options and I clicked on the world that I was trying to open and all my progress was reset. I also made sure I saved my Minecraft worlds beforehand exiting the game and this issue still occurs. This has been happening to every world I have made. Please fix this