Hey badgut. I empathize with you. The bewilderment, the second opinions, the insanity of it all. My docs couldn't explain my weight loss, bleeding, severity of my diarrhea, and fevers that I experienced for several months. I saw two GIs and an infectious disease doc in my town, and then went down to the Mayo Clinic to see the super-smartypants, hoping for some reliable news. Some said it could be the result of several parasitic infections I suffered several years ago when I was traveling in Africa; some said it could be Crohn's disease; but no one could tell anything for sure. I wanted to vomit all over them. I found myself in the ER every month or two for IV rehydration and narcotics (for the pain and to stop me up), then in the operating room when my gallbladder finally kicked out on me...I was a pathetic mess (have no idea how my friends put up with me). I tried antispasmodics, Imodium, probiotics, cholestyramine, fiber and calcium supplements, fish oil, narcotics, aloe juice, proton pump inhibitors, you name it. I eventually got so pissed at how much money I was spending on cure-alls that didn't seem to be doing anything for me, so I quit everything altogether. I suffered for a little while longer. Whined and complained to these wonderful people on this website 
. Tried to get on with life.
HOWEVER...slowly, slowly, I realized that I was starting to improve. Just a little bit, day by day. It took a few months for me to really notice that my diarrhea went from 20x/day to 10, then to 8, then to 5, and then I started having FORMED BMs, which really just blew my mind. I just about plotzed then. I stopped losing weight, and I stopped having 100-degree fevers every day. I haven't visited the ER since November 8, 2005. That is more than four months, a record!
I've had a few "relapses" - last week I had one of my so-called "garden-hose" days where I went 20 times, and I've noticed a bit more bleeding lately, and last night I was on the floor in pain - but really, on the whole, it has improved a lot. "They" may never figure "it" out, and I've gotten beyond the point where I need to have a name for it. I simply have some bad-ass guts. Proper, consistent treatment - instead of my current regimen of whatever I can get my hands on, be it Imodium, Pepcid, Tylenol, or the occasional Vicodin - would be nice, of course. Maybe someday it will be figured out.
This kind of things definitely increases your frustration tolerance, I'll say that.
Here's my advice - get a second opinion, and possibly a third, but don't get discouraged. I think more often than not our bodies will eventually begin to heal themselves, sometimes partially, sometimes fully. I really think that idea is underestimated sometimes. Good luck. You will get through this!