I had this problem before, if you also can't find your worlds in the world menu.
Something happened and it created a duplicate .minecraft folder (like if you reinstalled Minecraft). If you're on Mac, go to Finder, under the Go menu click Go to Folder, and the type in: ~/Library/Application Support/minecraft in the search box. You'll probably find your created world in that saves folder. Try to find your old .minecraft folder, copy all the old resource packs and saves from that into your new .minecraft folder, and enjoy.
If your worlds are showing up, but the new worlds just aren't saving in your saves folder, then maybe try to find your new .minecraft folder, copy the worlds that were probably saving into that saves folder, and bring them back to the old .minecraft folder.
If this doesn't work, then sorry !
