I've had diarrhea, headaches, lightheadedness and stomach cramps for five days. what could be causing it, and how do i treat it?

Bowel symptoms: There are many options for a variety of symptoms. It sounds most like infection of the bowel, viral or bacterial. The light headedness may be from dehydration from fluid loss. This could also cause your headaches. Follow up with MD to be reviewed. Hopefully it will get sorted out and you will feel better. Remember to keep up with your fluids.