How to recover a blank coreldraw files back to Orginal file?

I have been working on a science teaching files for 2 weeks and it was a 49 pages file that was about 300MB.

The problem is that i opened my file and i found out that it is just a blank page, but the file size still aroudn 300MB.

forget about the backup file. it is also corrupted .

What shoudl i do?