Can't sync my iPod Nano

I'm not able to sync my iPod Nano - I have 338 songs in my iTunes Library, and when I try to sync it, it doesn't pick up any new music - plus when I play it, it only play 124 of the 338 songs. It's nowhere near full. I tried to do a reload yesterday (1/25) and now it only has 24 songs on it. Everything is in my library though. What do I do?