You wrote an unusually articulate and thoughtful letter for someone your age. That tells me you are smart and creative. Without talking to you personally, I really can’t tell if there is something “wrong” or if you are an especially imaginative teen who hasn’t yet found an outlet for that creativity.
The good news and bad news is so much information is available about mental illness. Yes, it does help people sort out what they are dealing with. But I often worry about what I see in our culture as a tendency to make normal developmental issues into mental illness. It is normal for someone in the preteen through the teen years to “try on” different ways of being until they find out who they are. It isn’t usual to take it so far as to adopt an eating disorder to fit a character image. however, you indicated you have other issues with body image so it may be that the struggle with eating was more a function of that than the chameleon problem.
Since you have been “professionally diagnosed”, my best suggestion to you is that you go back to whoever made those diagnoses to talk about your concerns. That person knows you and will have the opportunity to ask the kind of questions a trained interviewer can ask to help determine what is going on with you. It will give you peace of mind to have your questions answered.
Meanwhile, I also urge you to stop reading about disorders and instead put your considerable creativity to work. Explore creative writing. Get invovled with a theatre group. You have untapped talents that deserve your attention.
I wish you well.