All Mobs Mysteriously Deleted When I Joined

I joined my world ready to use my new endermen xp farm when I noticed no endermen were falling into the kill chamber, I went to check out why when I realized there was no endremite even though I name tagged him. I went back to my base to get a new name tag but then I saw my villagers were gone and then I got worried. I usually keep some backup copies of my world but when I loaded them up they were also corrupted. All of the mobs, pets, and entities were gone please help I am heart broken fix it asap.My pets need me!!!!!!!!!!!!!!!!!!!!!!!!