my sister is 17. She completely passed out about a month ago and went to the hospital. They could not find out what caused it and we assumed it was a one time thing. Since then, she has been having severe, constant migraines and every once in a while will say she cant see anything and says that she feels hot and like shes going to throw up and cant breathe. She had this episode yesterday and collapsed onto the floor then was okay a few minutes after. She still is continuing to get lightheaded and naseaus. what could be the casue of it? should we be worried?