My husband has been suffering from change in bowel habit for the last 11 months. He suffers from frequent belching and 2-3 times a day soft bowel movement He was previously on cholesterol lowering drugs and this abnormality started just after 7 months from the day when he started taking the drugs. Can cholesterol drugs cause IBS? He recently did a stool test which didn't reveal anything. Should he go for a colon screening?