喝prune juice，一般的药店，grocery store都有卖的，应该很管用。

早晨空腹喝一杯柠檬蜂蜜水，一勺蜂蜜，挤半个柠檬汁，柠檬有加速肠蠕动的作用，对便秘有一定帮助。

it maybe stress induced, or that you are not eating enough fiber, if you get diarrhea and constipation interchangeably, i suggest you go to a doctor, it may be something called the Irritable Bowel Symdrome.