Macbook Pro

Hi I was using my laptop 2 days ago and it was really slow internet connection, didnt understand why so i turned the laptop off and on and when it came on message came up to say turn the laptop off which I did but now I cant turn it back on. It just has this downloading thing in the middle of the screen. have switched the laptop off for over 48 hours and tried again but no luck. To be honest I dont use the laptop that often as I have Ipad and work laptop but I have only bought my MacBook Proo 3 years ago, surely it shouldnt be doing this? I have all my music on there and dont want to lose any of it. Can anyone help and what should I do?