PERSONAL iPhone messages being sent to family members?

I imessage my friend (who owns an iphone) with my ipad fairly often. However, recently, for some reason, my mother, who owns an iphone and shares my apple ID, has been receiving our personal messages between one another. It's as if apple decided to include her in our conversation without consent. My messages to my friend go to my mom, and my friends messages to me go to my mom. None of us want this. What has happened, and how do I fix this?

You need your own apple id, I uses my Account for my daughters iPod and she kept receiving my messages