iPod touch iPod Touch 4G will not charge properly??

[mmell97]

I just got an iPod Touch 4g. I use the USB to charge as it did not come with a wall charger. The first time I charged it, it charged fine, but now whenever I plug it in it doesn't charge and nothing comes up on the computer either. The only reason I use the USB is to charge, as I do not have the latest iTunes to sync. When I run it flat and it asks me to charge I plug it in and a battery filled with a tiny bit of red shows and there is a lightning bolt underneath so I think it is charging, but after about five minutes this stops. So now I have just been charging when flat which gives about 20% battery, then I use that until flat and continue this cycle. Please healp, I have no idea what is wrong?