I had beaten just beaten the ender dragon and gotten my elytra when I logged back into my very developed world and all the blocks that I had every placed had disappeared. I deleted that world and used the backup that I had made 17 days before I had beaten the ender dragon.

I'm back at the end again (which should be for the first time in that backup world) and I got all the first time achievements for getting to the end. But everything that I did when I first fought the dragon is there. All the end crystals are gone and the dragon egg is gone. The portal back home is already active and the End City has already been raided.

Everything that I got at the end (dragon egg, dragon head, elytra) are all gone so I can't get them again. The backup was made about 17 days before I had beaten the ender dragon so I don't know how this could all be there. Please fix it. 

Username: Nox_ES73, Seed:495368034