Hi!
It looks like your file is corrupted, you can try to import it into an other scene, but if this doesn't work it may be lost.
To prevent data loss like this:
1. Do incremental saves (as often as suitable) and from time to time save or export in an additional format (like FBX or OBJ).
2. Delete history if not needed anymore (on single or all objects).
3. Create backups.
