It might be dehydration, it might be sleep deprivation, it might be hunger. Try and sleep, eat, and drink as regularly as possible. And if you drink soda, tea, coffee, or anything with chocolate, cut down- the caffeine dehydrates you.
If that doesn't work, see a doctor. I've heard of dizziness induced by head turning (or any change in position such as standing up or sitting down) as being an early sign of Ménière's disease (vertigo).
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Happiness is not something ready made. It comes from your own actions.
Dalai Lama