“What is causing dizziness?”

I am a 21-year-old female. I have been feeling dizzy for almost three weeks now. I am certain that I am not pregnant because I don't have experience. I sleep at 2 am most days and wake up at 8-9 am. I feel the world spinning whenever I am sitting or standing. I have to lean on a wall or an object to stop the dizziness. Even after I sleep, I still feel very lightheaded. I also noticed that my head is twitching numerous times a day. I only noticed its occurrence almost three weeks ago also, the same duration of my dizziness. Can you help me? I have no medical history and I am not on any medication right now. I haven't drunk any medicine since it occurred.