Doctor doesn't believe me?

I have been going to doctors for quite some time with issues about numbness in my limbs and muscle pains and such, and recently the muscles from being a high sch athlete started deteriating causing abnormally fast weight loss. I went to a different Dr two days ago and he is telling me that I exibit signs of an eating disorder like bullimia and dehydration, I currently wear braces, and I'm diabetic, I don't over or under eat, or vomit unless I'm really sick,

I know that he's wrong is there anybody that has a clue of anything with symptoms even close to his diagnosis to help me understand why he would just say that without doing any tests, I mean if I had an eating disorder why would I be waisting time and money to hear something I already know.

I'm desperate please help