Welcome, cmason

,
You didn't say how old your son was. If i were you I'd run, not walk, to another doctor who will take you and your son's care seriously. I don't know where you live or insurance information but I'd try to find out who specializes in lyme disease or infectious disease in your area.
Another source is this website:
http://tourettenowwhat.tripod.com/
The woman who runs it has a son with TS and also he had lyme. She is quite knowledgable about lyme.
I'm sorry that I don't have more specifics but keep looking and digging!!
Take care,
Tessa