OK, I'm gonna get pretty descriptive here. If descriptions of body functions gross you out, hit "back" now...
OK. If any of you are left... Are you truly constipated...or is it a matter of sluggish bowels?
"True constipation" means that it is very painful for you to produce stool. And when you do, it comes out in dry balls, pellets, hard and dry pieces. Usually small. It will be very painful to defecate (not just hard to push down, but downright painful.) Sometimes it will be accompanied by a rush of liquid fecal matter, and sometimes blood, because you've injured your anus (I TOLD you it was descriptive!!)
"Sluggish bowels" -- more typically a problem with those of us with MS, means that we'll produce stool -- usually large, sometimes soft and wet...but not very often.
Folks think humans are supposed to have a bowel movement every day. Actually, every-other-day is fine, every third day is acceptable. If it is less often than that, then you need to address it.
What happens with the sluggish bowels is this: the intestine is like a long coiled muscle. When it's working normally, it expands and contracts and the motion pushes the fecal matter through the digestive system and to the anus area, where other muscles start contracting, and signals from the brain alert you to the fact that you have to have a bowel movement. This all happens in such a way that you generally have time to pay attention the signal, and get to a bathroom. Normally people will "go" at around the same time every day, usually a half-hour to an hour after eating and drinking something, in the morning. But not always (See the paragraph, above.)
With MS, the muscles don't work properly. The intestine doesn't contract as it should (sluggish), and when the fecal matter gets to the point where signals are supposed to be rushing off to the brain, that circuit is "broke". So the fecal matter sits there for awhile..and then -- often suddenly, usually after ingesting food -- the trigger will go off, with VERY little time for you to get to a bathroom (bowel incontinence. Not a good thing). When you go, the stool will be large, relatively soft, lots of it -- not diareha, but just "wet" and a large quantity (as you've been "collecting" it for several days).
There are "bowel programs" that you can ask about, and usually the neurologist can refer you to someone who can work with you on this. Generally what the "program" is, is that indeed you increase fiber and liquids (not necessarily water, but liquids. Some folks find coffee works very well to stimulate the bowels). Try your grandmother's favorite -- prunes, or prune juice. (These days they call them dried plums, if you go looking for them in the grocery aisle.) And you sit on the toilet every morning at around the same time, whether you produce a movement or not. There are glycerine suppositories that work; I buy a product over the internet called ene-meez (I use one of these every other day) to trigger the bowel movement. (If you look up the ene-meez, there are two kinds; one a simple glycerine product which I use; the other more "medicinal", which I don't use.) Over time (several days to weeks) the system will get back to a more normal routine. If you *change* your routine, though -- miss a day when you normally have a bowel movement, it can mean that it'll take a few more days to get back on schedule, so you have to be fairly disciplined about this. I still occasionally experience bowel incontinence, but I've found that for me there are two "triggers" --
getting off my usual schedule, or ingesting food that has been prepared with MSG! (No more chinese take-out for me!!)
The nausea might well stem from the sluggish bowels -- fecal matter is, after all, fermenting food, and the fermentation produces gas, which can cause nausea, heartburn, and other discomfort.
Try to stay away from the medicinal stuff like ducolax (Milk of Magnesia is fine, if you can tolerate it! I can't!) There's a new fiber product out now which I haven't tried which they claim you can stir into any food -- the ad has them stirring it into spaghetti sauce and soup!, so if the fiber stuff is hard to consume, you might try that. Increase intake of fruits and veggies, too. Good luck!
Ain't MS fun???!! 