What Causes Severe Cramps Around The Ribs On Application Of Pressure?

I get severe cramps around my ribs or sides when I twist or turn or simply press down or exert gently. I don t know if this is gastrointestinal or muscular but they come and go and sometimes last for a minute or two. Sometimes it looks like my stomach is bulging until the cramp subsides. I ve started taking magnesium and fish oil, but neither really seems to help. I ve stopped going to yoga class because I would spend half the class recuping from the cramps...the spasms. My doctor has no idea what is causing this. Any suggestions? Thank you, Roshan