I Had My Second Preventive Colonoscopy On December 16, 2016,

I had my second preventive colonoscopy on December 16, 2016, which was completely clean, no polyps,etc. I prepped with GoLytely. Since the procedure, I have had very loose stools and/or diarrhea, neither of which existed prior. My bowel movements were completely normal before the procedure. The gastroenterologist prescribed Lomotil, which stops the loose stools but constipates me after 2 doses. He recommended I try the fodmap diet now. Given the abrupt onset following a colonoscopy, i would like to know what is causing the problem. Any ideas/advice/hypotheses would be helpful. Thanks.