What is this pulsing under my right rib cage? its a twitch and it lasts for 15 or so minutes a few times a day

Twitch: This appears to be an irritable abdominal muscle which twitches involuntarily but doesn't cause painful cramps or spasms. It isn't a pulsating blood vessel. It is similar to twitching of an eyelid. Muscle fatigue can bring it on. Unless you develop widespread muscle twitching seen in calcium or magnesium deficiencies, I doubt you have anything to worry about. See your MD if you still have concerns