I have had 2 months of diarrhea and vomitting, watery stooland abdominal pain. i got endoscopy, colonoscopy, biopsy and celiac disease test done and all tests were negative.there has been no proper diagnosis yet. what should i do?

Parasites: Has your stool been tested for ova and parasites particularly giardiasis and balstocystis homnis. If yes and all stool test are negative then irritable bowel syndrome diarrhea predominant is a possible diagnosis. You should follow up with your gastroenterologist.

Don't give up: See your primary care physician for re-evaluation of the symptoms and tests done so far, so that other diagnostic possibilities can be considered. You may have an intolerance to a medication that you've been on for awhile, or a food substance that's commonly present in your diet. There may be something in your environment at home or work that you are coming in contact with, causing the illness.

As above: Agree with other 2 answers. May need 2nd opinion from GI specialist since inflammatory bowel disorders may take years to diagnose. If no parasites (also giardia), check for dietary intolerances-most notably gluten or dairy. Try elimination diet (google it), and keep a diet/food journal. If you try gluten free give it at least 8 weeks.