No, DMDs work for people if they have RRMS, but it can still turn progressive. The theory is that MS is started in he first place by a pathogen and many people believe the pathogen to be C pn. Others believe it to be EBV. I had progressive MS and I had a C pn infection. I took the relevant antibiotics and my MS stopped: I regained the use of my paralyzed right arm and of my formerly bright brain. I have had no new MS symptoms since starting, ten years ago. I finished antibiotics in 2007.
If by your doctor you mean your neurologist, there is very little chance that he will support abx and your GP will usually tend to follow the neurologist's opinion. Sometimes, though, they are more adventurous: especially if you give them this site to read: http://www.davidwheldon.co.uk/ms-treatment.html
, or maybe the pdf file on the site.