to say how sorry I am for what you must be going through! I don't have MS, but I have chronic fatigue and/or FM. I have been taking Provigil, and it has changed my life. It gives me the energy I need just to get through the day. It is very expensive though. This year our insurance will cover half of it (Thank goodness!).
I don't know of any chair that helps with nerve or muscle pain. I just make sure that my work area is set up so that I don't have to do long reaching (i.e. for heavy books)and I take breaks when I can and stretch. I have my monitor set up on about 4 books so that it is right in front of my face so that I don't have to bend my neck at all to look at the monitor.
Have you ever read the "Spoons Theory?" If you haven't read it, it is very interesting! I don't know how to make a link, but if you just Google it, it is easy to find.