What Causes Unconsciousness?

Hi there, a while ago i lost conciosness at a function and had people immedietly bring me back and i went to the doctor a couple of days later and the doctor told me it was nothing.Only last week the i got really dizzy and felt i was about to loose conciosness again and i layed dowy fighting for air for 20 mins and i barely made it,I talked my way though it not wanting to give up.Since then I on a daily basis get dizzy n loss of balance,regardless if im standing,sitting or am lieing down.Is this a normal occurance in people?