Files "Missing"

Suddenly MacBook Pro (OSx 10.9.4) stops working, I did Force Quit; and when restarts my files and downloads are gone! Specially word documents (documents, excel, and ppt files are gone from the computer!!!) however, music, picture and video files are present. Even my drop box folder is gone from the computer!!

Files present in the Desktop are missing!

Files present in the My Documents are missing!!

Files present in the Downloads are missing!

Files present in the DropBox are missing!

Desktop background wallpaper changed to default!

May I know how can I handle this??