i-Message and FaceTime warning message

Hi there

I have been sent an email by apple to say someone has signed into iMessage and FaceTime using my apple ID. I am confused. I have never used these applications and I don't know what they do. It says I can sign into the apple ID and change the password. Question is, who signed into them using my apple ID?

I have received the same message from Apple after updating my phone and my wife's. (we both use the same Apple ID) But if you're not sure what's going on, then it's best to change your password.

First, how many Apple devices do you have and are you the only one who uses your Apple ID? If so, then your account was likely compromised and you should immediately change your password.

On the other hand, if you have multiple Apple devices and use the same Apple ID on all of them like me with my Macbook Pro, iMac, iPad 2 and iPhone 5S. Each time I login on any of those devices I get this message. I also get a pop-up on my iOS devices beyond the email..