I agree with the muscle tension, especially while driving. Try to remember to physically release your back and shoulders, and to breath deeply, in order to decrease tension. It's hard to do this at first, and you probably won't even realize you're all hunched up until you figure out how it feels when released. Try to do some slow stretching before and after as well.
As someone with a history of an M.S. diagnosis that turned out to be Late Stage Neurological Lyme Disease, I would stay aware of any muscle/nerve issues you have, and any other strange seemingly unrelated unexplained symptoms, but I wouldn't take one or two doctor's advice as the final damning word. Many, many people get diagnosed with M.S. and it's actually Lyme. Unfortunately most doctors don't recognize it, and it goes undetected. I only say all this because I can't bear to think of other people having to go through what I went through, when it doesn't have to be that way. I am not a doctor, but this is my experience.
This is a link on a documentary about Lyme Disease. It is very eye opening, and worth watching even just to increase your awareness for yourself and those that you love. They talk about specifically about M.S., Parkinson's, ALS, and Alzheimer's. This documentary, and the doctor that gave it to me, saved my life, after fifteen years of misdiagnosis. I hope I am not overstepping.
[youtube]http://www.youtube.com/watch?v=2JgR_Jfbhv8[/youtube]