my ipod won't charge when i hook it up to my computer, i have tried resetting it but that didn't work!

I have a ipod nano 7th generation and for the past three days my ipod has not charged. When I hook it up to my computer it says that its connected and it syncs. When I eject it my ipod at first is fully charged but when I go to listen to my music, it turns off or goes to were it is red. I have tried resetting it and restoring it. I have also tried not using my computer but that doesn't seem to work either so I'm starting to wonder if its the cord or the ipod itself but I am not sure.