Suggest Treatment For Cough, Abdominal Pain And Diarrhea While On Nexium

Started about four weeks ago, unproductive cough and sinus pressure. I have a history of sinus infections. Went to Dr and he put me on an antibiotic for 10 days. The cough continued however. The Dr placed me on an additional 40 mg of Nexium, I take 40 mg daily for acid re-flux and Barrett s esophagus. I have been taking double dose for ~10 days. Tuesday morning I was awakened by sharp abdominal pain and acute gas. Went to bathroom and had diarrhea. Stomach cramps and gas have persisted since. Diarrhea lasted until late Wednesday. i was unable to eat anything Tuesday, and ate dry toast Wednesday. My stool on Wednesday was solid black. I was able to eat dry toast, chicken noodle soup and a banana Friday. No bowel movement from late Wed thru Saturday morning. Saturday morning I had a soft stool, but still black. I did eat a regular breakfast and dinner today. I feel very bloated and have acute gas.