Many different conditions can cause fainting. These include heart problems such as irregular heart beat, seizures, panic or anxiety attacks, low blood sugar (hypoglycemia), anemia (a deficiency in healthy oxygen carrying cells), and problems with how the nervous system (the body's system of nerves) regulates blood pressure. Some types of fainting seem to run in families. While fainting may indicate a particular medical condition, sometimes it may occur in an otherwise healthy individual.
My best advice, follow through with the test the Dr. suggests to rule out causes of your fainting. I hope you continue to talk with us here in the forum and know we care.