While there's absolutely no way I can determine by internet what your doctors are having troubles figuring out, my first thought is cholecystitis but in reading that link, you would have additional abnormaltiies in your blood work. This was based on my assumption that your pain is to the upper right. If it's to the lower right, I'm thinking appendicitis but that too should show something in your CT or blood work.

So, unfortunately, I'm left with "if it worsens or doesn't get better then you need to go back to the doctor." It is possible that it was caused by a fleeting infection due to a virus or a bacteria. Most doctors will rule out the most common things and then wait. But, many doctors are not good at telling people when to come back for further testing/investigation which should always be when it fails to improve or worsens. In fact, in many ways it's often better to go back to the same doctor you originally saw because now he knows more about your condition in all the things that he ruled out.

Stephanie