iTunes trying to sync my library TWICE to my iPhone 4?

Everytime I try and sync my iPhone 4S to iTunes, I receive a notification that my iPhone "cannot be synced because there is not enough free space to hold all of the items in the iTunes library (32.44GB additional required)." Since my last sync, I have only added 4 songs to my library. Given that the capacity of the iPhone is 57GB, I have about 45GB of music in my library/on the iPhone, and iTunes is saying I need "32.44GB" more space on my phone, it seems clear that iTunes is trying to add the entirety of my 45GB AGAIN to the iPhone (57GB capacity - 45GB library leaves 12GB space, and if iTunes is trying to add my 45GB library again, it would be about 32.44GB short). How do I fix this, and get iTunes to recognize that it only needs to add the 4 new songs to the iPhone to have the libraries be completely synced?