It is so tough!
Getting dx'd quickly comes with alot of uncertainty. We differ a bit in regards to what brough us to the doctor - I had stroke like symptoms. After initial dx I went for a 2nd opinion to make me feel more confident. My doc suggested it, but I already had it lined up I was so sure he was wrong.
Maybe that is something that would help put your mind at ease too...Just a thought. It is tough - because you don't want to delay and risk further damage, but you feel you are not dealing with all some do :(
Don't be afraid to seek a second opinion. It's part of the diagnostic process. If your current Doc is uncomfortable with you seeking one, I'd be uncomfortable with them.
The second opinion idea is a good one. Like you, I went to the doctor for a numb leg, and a short time later I had a dx of MS. I wasn't looking for MS and neither was my doctor.
I understand what you are saying about wanting to treat the correct problem and not wanting to jump on the DMD. Get that second opinion and even a third if it will help.