when I open any of my worlds, everything is gone and is like as if it's a brand new world I've created even though it's not.

I'm unsure if my problem may be that ive made so many copies of a world, but now when I open any of my worlds, everything is gone and is like as if it's a brand new world I've created. Everything is just gone. I started making copies of my worlds to see if that fixed it. The copies seemed usable, but then did the same thing if I closed out and went back in.