Lost most of my songs on itunes after iphone backup and restore

I backed up my iPhone 5S to iTunes, reset my iphone, then restored the backup to the iphone. I had over 1000 songs in both my iphone and in itunes. Now, I have only 350 songs in my iTunes and much less than that on my iphone. Any idea where all my music went? (Everything else after the backup seems to be fine on my iphone)