In my case, several years ago things got really, really awful and I felt "possessed". Since years of therapy for lesser depression hadn't helped I decided to take the possibiity seriously and consult an exorcist. That didn't help, either, and in fact he thought that most people who felt possessed needed to see therapists. So back I went.

I'm not saying that others don't see my behavior as "evil" sometimes. For the most part I can inhibit the acting out, turning on myself instead. But when it does get out, it hurts them, and I'm not caring about anybody except myself at the moment, even though in general I do care about others. Nevertheless it's confusing.

There is a part of me who very definitely doesn't care about anybody but herself/me. I don't know if the notion of "parts" feels right to you, but maybe it will help. Bringing the "evil" part into therapy and having my therapist (a specialist in dissociative disorders) accept that part has been helpful to me, too.

I don't feel that I AM my diagnosis. For me, it's helpful to know what is "wrong" with me because something definitely has felt wrong inside. Not wrong in a social sense but wrong in a it's-not-functioning-well sense. It's helpful to me to see it as an illness, or a problem in development -- like maybe a fractured arm that didn't heal straight. And I'm way past blaming my parents for the blankety-blank fracture -- my parents did the best their (fractured) selves could do, doctors wouldn't have known how to set it anyway, at that time. But I'm hopeful that some of the new therapies will help.

Good luck with your appointment!!