I have had a change in bowel movements for the last six months;. sometimes diarrhea, sometimes loose,and thin?

All blood tests done by the doctor are normal and they say there is nothing seriously wrong. but my motions are different. sometimes s shaped, other times loose and bitty and other times bad cramps and diarhea and then other times really thin and flat. IBS is what docs think and because all bloods are clear, won't do colonoscopy. had an ectopic at the beginning of the year and it was discovered my bowel was attached to my womb. could this be the cause? help!!