YOU POOR THING!!! First of all, I second the "get a new doctor" order because you need proper testing and treatment and, more importantly, validation for your emotional distress too! I similarly had a rough exp with my first doctor, as I am sure the majority of people on these boards have as well, and I immediately sought out two new opinions!
What you are going through is so draining, emotionally and physically eesp when it happens on a chronic basis. I would suggest adopting the BRAT diet and drinking lots of peppermint tea and also fennel tea, too! They are very soothing on the belly.
I hope you feel better soon, and get validation for what you are going through. It is very difficult.