Another lady’s husband turned out to have [url=http://www.webmd.com/a-to-z-guides/giardiasis-topic-overview]Giardia[/url]. He had colonscopy and went to a gastroenterologist. He had blood tests.
He on tablets now. It is a water borne parasite.
He had continuous bad diarrhoea for 18 months but not a lot of pain.
You could look into thyroid too because if you have thyroid you can be totally constipated or the other way.