Welcome, Cordelia, nice to meet you. It sounds like your Docs think you have MS and you have been tested for all the other illnesses it could be, so, I would go with that and ask your Docs for meds to treat your symptoms when needed and live your life to the fullest.
When a real DX comes, will be the time to ask about Disease Modifying Drugs. In the meantime, enjoy all the benefits of your new home....the NeuroTalk Forum..