Ender Dragon crash

I have a World that I have played on for a month. It is survival and its a big project. I tried to defeat the Ender Dragon but every time I get close to him my game freezes. When loading the game back up, I was respawned without any loot. When I went back to get it, it was all gone/despawned. This has happened 5 different times and it really sucks. I haven’t seen any other reports of this that fit my description, so please fix.