Have you ever had bowel surgery at anytime in your life? Do you have any xrays of your bowels?
Something else to ponder...what is your external environment like?
In particular, what toxics are you around? New carpeting, new construction, mold, car exahaust, cleaners, etc. Sometimes the gut can be very reactive to certain compounds, or combinations of compounds and cause all kinds of symptoms.
Have you ever sprung for a gut diagnostic such as what Great Smokies Labs has to offer? Sounds to me like you could have an infestation in the small intestine. Another thing to consider is Amalgams and bacterial infection in your teeth that drips down into your digestive tract.
I can relate to "difficult" cases because I'm one myself but I find I learn alot and perhaps that is what my/your journey is all about.
Also consider emotional and spiritual aspects to this challenge.