What Causes Recurrent Attacks Of Dizziness?

Hi I had an episode of a very dizzy episode yesterday. I was aware that I was about to faint, losing coordiantion, and everything around me was spinning while I was driving. I drank water to improve my body fr I m this feeling. My body responded, I felt revived and a few minutes passed by, I felt this fainting episode coming on again, with everything around me spining and changing colour. 3 wks prior to this I was exausted, lack of sleep and feeling unwell.I was in ED , andnthe doctors said it was not a heart attack, blood tests were done and no evidence of heart attack. What could these symptoms be?