If your veterinarian hasn't already done so, see if he/she can run some blood tests, stool examinations, x-rays and maybe a few other tests to be sure what is causing it.
I've heard of vets using fibreoptic endoscopy. This can present a definitive diagnosis of IBD (Inflammatory Bowel Disease). The endoscope is a tool that lets the vet see the stomach and intestinal tract through a tube. The procedure is performed under anesthesia and most patients are able to go home the same day.
Prednizone, some antibiotics, and antiemetics (drugs that helps reduce vomiting), are a few I have heard that can help control IBD.
Good luck!

I've heard of vets using fibreoptic endoscopy. This can present a definitive diagnosis of IBD (Inflammatory Bowel Disease). The endoscope is a tool that lets the vet see the stomach and intestinal tract through a tube. The procedure is performed under anesthesia and most patients are able to go home the same day.
Prednizone, some antibiotics, and antiemetics (drugs that helps reduce vomiting), are a few I have heard that can help control IBD.
Good luck!