Can,t make a back up in the end.

I went to fight the ender dragon and won ,than I made a back up ,but I wanted to go get the elytra After I went do the small portal…?  I made a backup. I found a end city  with no boat.I went back to the last backup and I could not see any blocks. I was in a different viewing angle and my DPI  was very low.I went to the back up before I went do the small portal and everything was fine.After I was ready I went on a hunt for a elytra again.While I was bridging I thought I would need to make a backup and I did .When I came back I thought the same thing again.I went do the backup I made and it was still there .I tried like 5 times but nothing . Still to this time I have not get to play my world again.Hope you can fix the bug and help me to get back my world.