It could reveal a number of different
causes for your dizziness, fatigue, and
fainting (sometimes GI sometimes are even related). These disorders (including vasovagal syncope) are under the umbrella of "dysautonomia" and you may want to post in the dysautonomia forum here on MedHelp to find out more about testing for autonomic disorders as well as the types of conditions that could possibly cause the symptoms you're describing.