None of my music shows up on my iphone

[venomX]

In the libary section i can see all of my music but under the iphone parth of music there is none of my music what can I do to fix that?

[AU girl]

In the libary section i can see all of my music but under the iphone parth of music there is none of my music what can I do to fix that?
At first mine had it and then I changed what I wanted to sync and only 5 songs synced and a little box came up saying it was having difficulty w/itunes music. I think overload, so I will try tomorrow and resync