It's great to hear that your doctor supported breastfeeding. Definitely breastfeeding helped me with MS symptoms. I also became much worse when I stopped.
But moms with MS don't have to choose between breastfeeding and MS meds. Copaxone, for example, is considered generally safe by breastfeeding experts. I wouldn't expect neurologists to know this since they're experts in adults and neurology, not in baby nutrition.
For the best advice on medication and breastfeeding, a great source is a lactation consultant or a breastfeeding pharmacologist. Here are a few quick links to check out breastfeeding and medications.
Great overview from Dr. Jack Newman:
This article is from the American Academy of Pediatrics and gives charts of accepted meds for a breastfeeding mom (includes interferon, baclofen, gadolinium, for example):
http://aappolicy.aappublications.org/cg ... 8/3/776#T6
An overview of how meds get into the milk/baby (this site is great overall):