I got that pain from Ranitidine, then PPI's and now from many types of pills. It is a dull cramping pain in the RUQ. I have had all tests, everything comes back normal. My dr's say don't worry about it, and think I should not do anymore tests since everything has continually come back ok. They think its probably hypersensitivity or some benign pain.
I feel for you, trust me. I was worried about this pain and continue to now and then. I have had it for over a year now, on and off. It usually only comes for a few days every 3 weeks or so, but when I am on Nexium or some other pills I have it non-stop until I stop the pill.
Wish I had an answer for you as to what it was. A year ago I was in your shoes, trying to find someone who had it and had it diagnosed to give me an idea of what I had. If it is any consolation just know that mine, although undiagnosed, is supposedly benign.