iTunes won't add music to iPod and other issues.

I own a 5th generation iPod Touch 32gb and recently I have encountered issues with it. About 2 weeks ago I attempted to add a new song onto the device. Now iTunes used to allow you to select which songs from the library to add but now it seems to add them all, which is fine by me, however after I synced the library the new song didn't add. So I didn't worry about it but today I attempted to fix it. Firstly I cleared up space on my iPod so there is definitely enough room, however I did discover that the 'Other' section of usage was 8gb and the photo usage was coming up as 2 gb when it would have been actually around 6. Secondly, I reinstalled iTunes. I also deleted all the music off my iPod and synced it. However after that I noticed that some of the albums have disappeared off the iPod and alot of the songs that are listed play but have no audio coming out. After this I tried backing it up which was to no avail. What on Earth is the matter? Is it my iPod or iTunes? Should I do a factory restart on my iPod??