who is FaceTiming on my iPod touch

No idea. I'm not even sure whether you mean that someone in your household is using your iPod to send messages with your ID, sending messages from somewhere else but with your ID, or whether someone you don't know is sending you messages.

I suggest that you read this article from user John Galt: Writing an effective Apple Support Commun… - Apple Community and then write a new question.

In the meantime, if you believe that someone has access to your facetime account, I suggest that you change the password for it, thereby denying that person any further access.