今天早上李华觉得肚子痛，妈妈带他去了医院，怎么回事呢？请根据下面的要点提示，写一篇80词左右的短文，对李华的病因和医生的建议进行介绍，可适当发挥．开头已给出，不计入总词数。

Time: this morning

Reasons: unboiled water （生水）；junk food…

Doctor's advice: never drink dirty or unboiled water; wash hands often; eat less junk food…

    This morning, Li Hua had a stomachache.