It could be many things. It could be from slouching or sitting in a way that is causing the diaphragm to be compressed. Do not try to over straighten, just think of relaxing the muscles and allowing yourself to fall into a natural position. It could be injury from working out and doing crunches or other movements. It could be a stomach ulcer.
Another option is to blanch green beans quickly. Blanch your green beans by boiling them for 3 or 4 minutes. This removes the skin of your green beans. You want your beans to be somewhat tender, yet have a little bit of crispness to them. Determine the crispness, by how long you boil them.
Cook green beans directly in boiling water or broth. Place cleaned and trimmed green beans in boiling water or broth, then bring the water back to a boil. Cook the beans for four to five minutes, or until they are tender but crisp. For a softer texture, boil the green beans longer.