It sounds like you are going the right route. I'd wait to find out if the lyme test showed anything and if it's negative I would definately get a second opinion. Have you seen a rheumatologist? You might have lupus which can also explain some symptoms. A negative spinal tap does not mean you don't have MS. Also, have they checked for b12 deficiency?
Please keep us posted and good luck!
"Life shouldn't be a journey to the grave with the intention of arriving
safely in a pretty and well preserved body, but rather, to skid in
broadside, thoroughly used up, totally worn out, and loudly
shouting...."Wow! What a ride! Thank You Lord!!!"