Forrest, I am hesitant to say "forget about your liver," after what I went through. I had a primary care doc who was following my known hep C with LFTs every 6 mos. and an ultrasound every year. In '04, I was having ULQ pain, but nothing showed up on US. I continued to complain of pain in the following year, but got "blown off." My LFTs were the same as always (elevated, but not drastically.) She was not doing Alfa fetoprotein, which I should have insisted on. At any rate, with the next yearly US done in April '05, there was a diagnosis of a large tumor (6 1/2 inches at the longest point) in the right lobe of my liver, thought to be hepatocellular carcinoma (it was.) I switched to Mayo Clinic and have had remarkable success with just two treatments....cancer is mostly dead.
Therefore, I would insist on an MRI. Tell them that despite the CT scans, etc., you are having upper rt. quadrant pain and want to rule out liver problems.
More than likely, it IS IBS, but I would get an MRI to be sure that your liver isn't involved in some way.
Good luck and let us know!