music not syncing to iphone

Hi - i'm having an issue with my iTunes library syncing to my iPhone. It was fine, but my phone died and i had to get a new one and for some reason now that i'm trying to sync my iTunes to my new phone, there are a lot of songs that are grayish color with a circle beside them and won't play (from the computer) and they're not downloading to the phone. The songs i am just now purchasing are not all showing up in my "purchased" album either. I'm not really sure what is going on. If i unplug my phone from my computer and just look at my iTunes in general, it all looks fine, its only when i hook the phone up and try to sync it. Any ideas??