Except the weight loss I have many of your symptoms. Mine started at least a couple years ago. I’m sick to my stomach all the time, I have a lot of pain in my stomach/abdomen, everything can set it off, including drinking water. I too have had many tests including an Octrio(sp) Scan and a MIBG scan with the outcome of no tumors. While that is good news it doesn’t help.
On top of that ALL the doctors can say is “Go to the Mayo Clinic”. That is a total cop out in my opinion as well as bullshit. I wish I could get away with walking from my problems by telling people to go somewhere else.