What should I do if my music app on my 3gs iphone isn't working?

My iphone 3gs isn't playing the music on my music app. It suddenly stopped after I restarted it on my computered and used icloud. Now the music won't play that's just on my phone. Pandora and other stuff plays fine but the music I bought myself won't play. Even on my idock clock it won't play. Please help, it's getting really annoying and frustrating living like this. I love technology but now I'm starting to hate it.