Blocks disappear after being placed, previously broken blocks come back

After I updated to the latest update, everything was fine for a few days. Then suddenly blocks come back after being broken, and placed blocks disappear after a few seconds. The inventory is slow to respond when I press open, and worlds take twice as long to load up or save and exit. 

Update: now the world won't even load, it crashes Minecraft after 5 minutes of loading. Since this is my 3 year old creative world, I have multiple backups. But even the oldest backup started to get more and more buggy the longer I played it until it was just as bad as the original. Is the world somehow corrupted and I no longer have a version of it that isn't corrupted?