corrupted 1.16.1 hardcore world

so, I started up the Minecraft launcher after I reinstalled it, I played before I put all of the worlds in an old Minecraft launcher, so, I got all the worlds, and pasted them into the new Minecraft launcher. the world appeared, and everything was totally fine. then, I started up my hardcore world.

but, when I started playing it, I started losing health automatically.

I quit, and then I rejoined the world. it happened again, thankfully, I broke the dirt that is was suffocating in, and a dug a little area underground. then, I went to the surface and saw that all of my items had saved, but, none of the structures saved. I don't mean that the world is totally stu=ructureless like without trees.