Why is she every where?

My boyfriend has this ex. She's his high school sweetheart. They lasted four years. She was just a huge part of his life that almost 3 years later, she's still just every where. Around his family's house. He's called me her name( twice in the beginning) , his family has called me her name. Pictures of her around the house... They had been separated for about two and him and I have been together for 7 months. Am I being ridiculous for being kind of pissy about this and if I am, how can I start to feel better about this? I know he doesn't love her anymore, we've talked about it. But I don't know. It bothers me.