While you're trying to figure out what is going on, if you're not sensitive to ginger (like I am), you can make a ginger tea and see if that will help you out with the nausea. It is inexpensive and easy to do:
Fill a small saucepan (about one qt) with water and bring to a boil. While waiting for the water to boil, peel and slice a one to two inch piece of ginger root and add it to the water. Once the water comes to a rolling boil, turn the temperature down to medium high and leave the ginger cooking in the water 'til about half of the water has evaporated. It sounds like it would take a long time, but this takes hardly any time at all. Try the ginger tea without sugar first. Sugar causes inflammation and can aggravate your symptoms. If you must add sweetener, don't use the fake stuff, because the chemicals will aggravate your problems, too. If you must use a sweetener, don't use a lot. It is best to not use any sweetener in your case.
also a celiac blood test might help as well. IBS-D can be a bunch of things...from colitis/chron's/food allergies/parasites/bugs...
hopefully it'll go away..
couple of things...
could be giardia..like any recent travel? Bad water...that flu thing that scared everyone N1H1 thingy...
could be a food intolerance/allergy issue as well. Like it happened to me over night..just out of the blue, i'm nauseated weak/can't sleep...anxiety ridden..turns out it was soy and something else for me..but IBS-D it could be now an intolerance to wheat/milk/fructose...
i'd avoid those 3...if not then it could be something you ate or a bug/stomach virus going around. Maybe head off to the grocery store and get some lactaid pills (cheap) and possibly some puffed rice or rice chex and give that a go for breakfast...or not eat any fruits for like oo..4 days and then buy some pears and apples and chow down..if you get sick it could be fructose intolerance.
Anyway just some ideas. Did they do a urine test on you? Sounds like sort of like a UTI in ways too...