Problems syncing ipodto itunes

I have recently purchased two albums from iTunes but when I press sync, nothing happens! I have plenty of room left on my ipod (classic 120gb). I've recently switched laptops due to m old one dying and have managed to transfer the albums I purchase but not the CD's I've uploaded, another annoyance! I've looked for answers and the only guidance I can find is to auto sync which wipes my ipod therefore deleting all my CDs which I don't want to do. If this is the only way to load brand new purchases to my ipod without losing all my CD music then that is very poor. Please can someone help???