There are a number of programs to tidy up your iTunes music library. Not necessarily Apple software and there is usually a small cost but do a google search and you will find them. Good ones also do things like sort out your album artwork.
A couple of links for you -
How to find and delete duplicate songs in your iTunes library | iMore
Tenorshare Music Cleanup ? Clean Up iTunes Library and Fix Missing Album Information
Lots more out there.
Cheers,
TimJ.

