my ipod 4th generation won't sign into IMessage or FaceTime?

My ipod 4th gen on iso 6.1.6 has recently signed me out of Imessage and FaceTime and when I go to SETTINGS, MESSAGES, I enter in the information for my apple id and password and it takes me to a verification page where I enter the email I would like to use for my device. It starts to say verify and then sends me back to MESSAGES under SETTINGS where I need to sign in again and repeats. Help please.