You might try increasing your daily intake of fiber and water. My mom usually takes 2-3 days to go because of her Parkinson's.
My Japanese MSer bud put me on to Apple Cider Vinegar to increase metabolism. His doctor has him take it. I take 2 Tsp diluted with 6-8 oz of water within an hour of getting up in the morning and within an hour of going to bed. I can count on a bowel movement in the morning and evening. I do not need it to "go", but I have noticed it makes me "go".
As it increase acidity, you want to make sure you are getting sufficient calcium intake to protect your bones and potassium too. Bananas are a good source of potassium.
For me, MS has always meant frequency increases of BM when my body is under attack.