I have recently bought a Sony Xperia U, and downloaded the spotify app. I have premium. But when I try to play a song, it stops and starts, like a CD skipping, and in general when searching for music it is sluggish. Other apps like youtube buffer videos perfectly, and browsing the internet is fine. I downloaded an internet speed monitor app, which showed I could download at a max rate of 10mbs apparently, so it can't be my internet?

I have had a look through the spotify settings and it's set to "normal quality", not high or anything. 

Since I pay for and rely on spotify I would really appreciate if someone could give me some suggestions, as I am very new to android phones, thank you!