Hi there ..
I'm so sorry to hear that you are having such a crap time of it ...
I sympathise, but then, you don't need sympathy as much as answers and correct treatment ... you were right to insist on a different Medical Doctor other than he that is treating you for your eating disorder .. I wouldn't like to say that this is all connected, as you aren't supplying your body, organs, bones, muscles etc with the nutrition that is requires.
When you see this other doctor tommorrow, please make sure you tell him everything ... right down to the pills you have been taking, and the twitching / spasms.
BTW .. Arthritus means wearing of the bones, where they become weak and worn down ... I'm glad that came back negative.
I can re-post this in the 'Eating Disorders' forum, just for now, so that others that also have been or are experiencing the same symptons as this, can advise and help support you ..
Take care and stay strong
Ginger