iMessage Not working on iPhone 3GS or iPod 5th Generation..HELP!

I am very new to the apple world but when I first got my ipod I could send imessages to other users no problem. When I first got this 3GS (yes its updated to version 6) it would send imessages no problem. Now, for the past several days I can get neither of them to send imessage. iPod won't send at all but 3GS converts to SMS. It looks like everything is activated correctly and I have all the correct information so I am confused as to why its wanting to act a pain. ANY help will be much appreciated.