HI Well come to HCM Thank for choosing HCM, I had gone through the history given here, I could say that it is the typical history of IBS (Irritable bowel syndrome ) it is not the pathological changes that causes the symptoms but it is the depression, anxiety, chronic fatigue syndrome could be the cause, it is the subtle symptoms may includes diarrhea, constipation or both. Young person are more vulnerable life style change, apprehensiveness, loss of confidence and other psychological factors are responsible for this. Once the disease being diagnosed then it can be managed with anti-depression and diet restriction, here the differential diagnosis is matter of concern indeed. hope this information helps.