I hope someone can come up with something here. I have the same problem. It started six months ago with a 24 bout of vomiting and diarrhea.
I had been to the doctor on Friday for a tendon tear and weighed in. I got sick Sunday around 10 and spent all day transferring from sitting on the toilet to leaning over it. I called in sick on Monday for the first time I can remember (I'm 46) and had lost 12 pounds when I weighed in at the doc. She said it was likely a flu, gave me something for the nausea and diarrhea and sent me on my way.
I stopped vomiting but the nausea didn't go away for over four months and I still have it 1-3 days a week (not quite as bad as it was before).
I still have the diarrhea. I may have 2 slightly more solid stools a week (still very soft) but usually followed by 6-7 watery stools (high pressure) in 2-4 hours. I have been tested for parasites, infections, you name it. I specifically asked for C-diff because sometimes it is very mucousy and... aromatic.
I work in a nursing home and have smelled c-diff.. I would have bet a weeks pay it would be positive but it wasn't.
The slightly more solid stools started when I started taking Metamucil. It seems to form a slight cork but that is all.
In a related note, I started a medically supervised, all liquid, diet two months ago. One of the side effects of the diet is constipation it had no change on my situation. I have lost nearly 50 pounds though so that is good.
Any ideas would be greatly appreciated.
Ken