What Causes Intermittent Pain In Right Quadrant Of Abdomen?

I have a pain in the right quadrant of my stomach that comes and goes, sometimes feeling like a knife has been stuck in me. My doctor has ruled out appendicitis. Colonoscopy and sonogram have revealed no reason. My doctor says it may be scar tissue from some previous surgery, but the only surgery I have had is C sections for the births of my 3 children, which is not close to the pain.