It's done it again?

My iPod Touch 5G has lost all its music again after synching with my laptop. This is the third time it has done it and I have to transfer my music from the laptop manually as it seems to have a problem with the synch mode? With over 1000 tracks of music, it is taking me ages to transfer them over. I have re-set the iPod back to manufactures settings, still no joy. I have removed iTunes from my laptop and installed the latest version, but still I get the same problem once I have managed to get all my music on to the iPod. As soon as I close down iTunes on the laptop, the sync bar shows for a few seconds and then closes down. When I check my iPod I find that all my music, except those that I have purchased, have been deleted? Why? Any help would be appreciated.