left sided abd pain w/gas & bloating

I have 2 gastric ulcers with an eroded esophagous. I have been on nexium for 18 months with good results. The past 3-4 months I have had left sided abd pain with bloating and gas. Very painful. Now I have noticed that the pain is even worse after and during eating. I have the gnawing and burning from the ulcers plus these other symptoms. I have ahad a colonoscopy  with negative results. The M.D. suggested I continue with nexium and use Pangestyme EC tid to see if this helps. He does feel that this has something to do with the colon and possibly lack of enzymes to aid in digestion.