Lightheaded/shaking feeling in my head?

ive been having this weird lightheadedness/shakiness in my head for a couple of years now on and off. and i still have no clue what it is. i have been to the doctor for it a couple of times now, but they say im stressed out but i really am not, and prescribe me motion sickness medicine(doesnt work). my bloodwork comes out fine, but still dont know whats causing it. help??????! please