All the content from my iTunes library has disappeared

The other day I went onto iTunes and everything had disappeared from it except for the music in the Cloud. All the music is still intact in the folders on my computer and when I double click any song it reappears on iTunes but without any information like number of plays, and I obviously don't want to do this manually for every song as I have nearly two thousand. I synced my iPod with iTunes again but no message came up and the music is still on my iPod, as if it is only 'hiding' on iTunes. I'm not sure if it's something to do with the fact i got a new iPod a few days ago, but iTunes worked perfectly when I first got it so I'm confused about what's happened.