Iphone won't sync. Just says backing up?

Whenever I just plug my phone into my computer it just says backing up when I try to put some music on?

Go to itunes settings and check whether the automatic backup is turned on and try it turn it off

I don't know about all the iphones but on the 5 you have to go in to the music tab after you're at the summary page. Once there you have two choices sync all of your music to your phone or only sync checked. If you choose checked then you got to go and check what you one installed. Once your ready then just push apply at the bottom