Welcome to ThisIsMS, JocieS.
To answer your specific question… I have not tried medical marijuana for my MS. But please allow me to express a few ideas that may be related to other information you have shared.
Concerning a weight gain:
My ideas revolve around insulin. (As I share my ideas, remember that I have no medical background.) The following sentence, however, is scientific fact: Pregnancy is one of two times in life (Puberty is the other time.) when a woman is in an insulin resistant state (her body is producing increased insulin in order to put weight on the fetus). I suspect that the mother's body often does not revert to normal secretion immediately after delivery of the baby. I believe that your pancreas did not return to normal insulin production after your last baby was born. I believe your pancreas continues to produce excess insulin today. If you request your GP to order a "fasting blood insulin test" (which is NOT the same as a glucose/blood sugar test), this problem can be ruled out if your insulin level is in the optimal 3 UU/ML or lower range.
I wonder how soon after your last child was born your symptoms/diagnosis was made.
Pregnancy is only one cause for excess insulin production (and, of course, cannot be the mechanism in men, children, virgins, or menopausal women). Other conditions can cause excess insulin: Diet (gluten, carbohydrates, artificial sweeteners, trans fats, MSG, BPA) can also trigger increased insulin levels - whole wheat bread and artificial sweeteners can do this more than common table sugar! Pancreatitis, virus/bacterium, even increasing age can cause excess insulin (hyperinsulinemia).
The Dr. Oz Show featured the author and book, Dr. William Davis and his book, Wheat Belly
Video Pt 1: http://www.doctoroz.com/episode/are-you-addicted-wheat
In Pt 2 the fact that wheat causes a blood sugar spike GREATER than a Snickers candy bar is pointed out!
Dr. Oz article, "Celiac Disease: The Advantages of a Gluten-Free Diet"http://www.doctoroz.com/videos/celiac-d ... iet?page=2
"Researchers now believe that Celiac disease may be more common in the United States than previously thought, especially given the high rate of misdiagnosis. There are now reliable blood tests to help your doctor determine if you are a Celiac sufferer. Because Celiac is an autoimmune disease, people with Celiac have abnormally high levels of certain antibodies (anti-gliadin, anti-endomysium and anti-tissue transglutaminase). Your doctor can test for these antibody levels and may confirm the diagnosis with an endoscopic tissue sample (which involves using a tiny camera to look at the lining of the intestines.)
Not only can wheat/gluten stimulate insulin (and insulin is necessary for a human body to put on weight), but wheat/gluten can damage the small intestine and interfere with nutrient absorption. This damage can occur in people who are simply gluten sensitive; it is not necessary to be at the extreme end (celiac disease) before this damage happens.
By the way, antidepressants also interfere with vitamin B12 – a B12 deficiency can have neurological symptoms and mimic MS. I hope your doctor tested you for a B12 deficiency. Chronic pain can be a symptom of B12 deficiency, and it can be a symptom of gluten sensitivity.
We wish you all the best.
My hypothesis: excess insulin (hyperinsulinemia) plays a major role in MS, as developed in my initial post: http://www.thisisms.com/forum/general-discussion-f1/topic1878.html "Insulin – Could This Be the Key?"