Since I was about 10 years old I have been having these fainting spells. I never have them sitting down just when I am standing. I feel a pressure in my head, then my vision goes black, I hear a roaring in my ears, and they last for only seconds. When I come back I am slightly confused for a second then my head hurts a little, my heart is pounding, I sometimes have coldsweats, and my breathing is faster. I am 24 years old and in the last couple years they have been getting a little worse. I'm 4'10" and about 110 lbs max. I sleep ok, don't really drink but maybe once or twice a week with a beer or two, I recently stopped exercising but had been exercising everyday for the past 3 years. I've started to have little spells sitting down now and i'm concerned about what it is. I've been to the doctor a couple times and got diagnosed with syncope and was told it would go away in my early 20s. My grandmother has something to do with high potassium with similiar symptoms. What is wrong with me?