Music will not download onto iPhone?

My iphone won't sync new music to it. When i plug it in, it syncs the old music, but not any of the new cds i put on. I tried deleting all the music off my iphone and resyncing everything but it still isn't working. I also tried restarting my iphone, and i checked for updates for itunes and my iphone, but both are up to date. The music just will not sync!
what do i do now?

You have to reset the phone by witch go to settings>genral>reset> erase all content and settings. An DO NOT restore from a back up but START AS NEW IPHONE. That will reset all of your settings and it should catch the new music as the old songs too. But make sure you back up your photos to your computet or to icloud.