The carbonation in the Diet Coke isn't good; neither is the artificial sweetener. Are you drinking the kind with caffeine? If so, though caffeine is a no-no for IBSers (and many other people as well), your body could have become addicted to it. Your colon may think that it needs it to function properly. If so, you may want to ease off of it gradually (I do agree to ditch it), not cold turkey.I got IBS really bad a month after I stopped drinking coffee cold turkey. 'Course, there were lots of other factors involved, too, but I'm pretty sure my system depended on the caffeine as a laxative. I perhaps shouldn't have quit cold turkey.