waywhen, It sounds like Diverticulosis to me, so the CT Scan will show it and so will a a scope. I had it and it was very painful that I was doubled up in pain, I had it so bad that they did a bowel resection and if they had taken another 2 in. I would have ended up with a bag, so I am thankful for not having one of those thing.
So hopefully your tests will give you a answer. Just hang in there, you have all the symptoms that I had. Good luck to you. Leslie