All of my world disappeared for no reason that I can see. My texture packs and addons are fine. But the worlds are all gone.

Today I got on mcpe. I downloaded a new add-on but that shouldn't have affected it. Mcpe loaded up but all of my worlds were missing. It offered the choice of switching my storage and I tried that. My texture packs and add-ons are still there but all my worlds are missing. I checked both of them. My worlds have just simply disappeared.