Case of the ex

Obviously everyone comes with a relationship history and exes. As a rule, there's usually one that sticks around for a while, at least in your head, and in a new relationship you both need to come to terms with his or her existence. But how far should this go? 

Obsessed with his ex 
Like Rebecca in the Daphne du Maurier novel, the ex becomes an obsession - for both of you. Either in a good or bad way, she's left a real impression on him and her presence hangs over you: his friends still talk about her, and wherever you go he seems to have taken her there before, or has memories of her there. This mysterious ex can start to seem like someone really special, and you start to doubt how much he can really love you after her. You start to obsess about her, what she looks like, even try to copy her style, and you quiz him about her too much. Her ghost is haunting your relationship, and three's a crowd.

The ex that won't go away 
OK, so she's still part of his circle of friends, which means you have to see her every time you go out. Fair enough, you're all adults - you can handle that. But she doesn't seem to accept that it's over between her and him: she's always finding excuses to call him and see him. What's more, he seems okay with it. You start to ask yourself whether it's you or her he wants, and get angry with him for not setting her straight. This leads to you losing your rag with him and things getting nasty.