Every few weeks for the last 4 years I get severe muscle cramping, or spasms on the bottom of my left rib cage. Visually when it starts I can see the muscle protruding out as though it were a bone, it gets very intense to the point that I cannot sit still until it relaxes. The pain is somewhat severe in the muscle almost like it's on the verge of exploding. Any ideas on what might be causing this? It continually does this regardless of diet and exercise. I am a healthy 29 year old male with relatively no health problems my whole life.