My Apple Id being used to sign in to Facetime and Messenger on a new iPod Touch

A couple of weeks ago, I got a small pop-up notification that my Apple ID was being used to sign in to FaceTime and Messenger on a new iPod Touch. I have never used FaceTime, and my two iPod Touch devices, both off, were sitting in sight of where I was using my MacBook.

I immediately changed my Apple ID password.

It just happened again. What should I do?