I Have Been Having Weak Dizzy Spells Since June. I

I have been having weak dizzy spells since June. I break out in a clammy sweat no matter the temperature. I am thirsty after these spells. I have received IV fluids for dehydration and worn a heart monitor for 48 hours. I have to sit down and rest after these times. They happen every time I am on my feet for more than -5 minutes no matter the temperature.