What you have on your computer is an iTunes library. Your "account" (Apple ID) is associated with the iTunes Store (making purchases), and is separate from your iTunes library. So, signing in with your Apple ID in iTunes does not affect what is in your iTunes library on the computer.
So, you are saying that your iTunes library only has two songs now, when it previously had over 900?
Anything special about the two songs that remain? For example, are they the last two songs you added?
Do you still see your playlists?
Look here: /[your user home folder]/Music/iTunes/iTunes Media/Music/
The path may be somewhat different depending your OS. If you did not change iTunes settings, your song files should be stored there, in sub-folders organized by artist name and then album name. When you look at that location using the Mac's Finder or Windows Explorer, do you see all of your song files there?