Sometimes i get light headed, hot and start sweating, i then feel sick and i vomit, 5 minutes later i feel fine, i have fainted before what could it be?

Needs evaluation: Your symptoms really would be better evaluated by a physician who can do physical testing and possibly order an imaging study of your head and neck. The symptoms you mention really can point to a number of processes and narrowing that field down in a forum such as this would simply be impossible without being able to physically evaluate you.