iPhone music doesn't sync

I was trying to sync new music from my macbook to my iphone, that deleted every album artwork i had on my iphone. I tried deleting all the music on my phone to sync it again but it doesn't work. On my computer it still says I have all the songs on phone when I deleted them all. When I try to sync my phone to my computer it says I don't have sufficient memory when I just deleted 7.9GB of music (I love music).