iPhone 6 iOS 8.1.3- Why has my all my music NOT downloaded onto my iphone?

iPhone 6 iOS 8.1.3- Why has my all my music NOT downloaded onto my iPhone? I have recently changed from my iPhone 5 to 6, All my music that is situated on my Macbook as well as iCloud, has not downloaded fully on my iPhone 6.

When i view the tracks (approx 3900), most of them have a little ''cloud'' next to the track no. which suggests that the trac needs to be downloaded first.

I have plenty of space available (43GB), yet the tracks has not downloaded fully, despite syncing with my Macbook quite often.