What Causes Sleepiness, Dizziness, Vomiting And Back Pain?

Question : My 19 year old grandson has been having episodes 2 or 3 times a year for the last 4 years. This started when he was 15. Episodes last from 4 to 10 days and include: sleeping up to 22 hours a day, mental confusion, child like state, dizziness, vomiting, complains his back hurts. Over the years we have taken him to family doctor, emergency rooms, neurologist, and lots of testing was done. The only diagnosis has been recurring mono (which AI Dupont later said was not) and possible marijuan use (which the neurologist said would not possible cause impairments for 10 days) We are so frustrated and don't know what else to do. He has not health insurance and has a job he really likes but might get fired as this is the second time he has been out of work for extended period with no diagnosis to justify the missing time. Now XXXXXXX is usually very outgoing, sassy, busy, running here and there and socializing and loud and boisterious by nature. Totally changes when he gets these episodes. He becomes quiet and has a stunned look on his face. has trouble remembering date, time, what he ate, just like the lights are on and no one is home. I have tried to do extensive research and the thing that usually comes up is Kliene Levin syndrome but it is very rare and hard to find anyone who can diagnose it. 7 days ago XXXXXXX came home and said I don't feel right, I think it is happening again. Since then he has slept and slept and not gone anywhere, Says he is too dizzy to drive. too tired to care, Not talking to his friends on anything. complete state of shut down. Each day he says he is coming out of it little by little but then feels dizzy, vomits, and calls out of work again and goes back to sleep. When these spells are over he will over the course of days slowly become more alert more awake and trying to figure out what all happened when he was out of it. Then he will be right back to his normal loud and busy self for months. Till boom it hits him again. I really don't know what to do. don't know if it is mental illness or physical, a brain issue or hormonal. I am really lost here. please help, Have you ever seen this before and what is the likely cause? What kind of doctor should we seek out?