You may be havig a condition called BPPV.
BPPV is caused spontaneously due to a condition of the inner ear and is associated with vertigo on movement of the head. You should see an ENT doctor for this. You will need a clinical examination plus tests like the Dix-Hallpike tests and ENG. You should discuss these tests with him. You will need antivertigo medicines plus need to do some mild exercises.
You should take OTC Cap. Benadryl 50 mg twice daily, this has an anti-dizziness effect. It may cause sleepiness.
Also check up this site for more information on BPPV and its treatment, you should do the exercises described in this site at home : http://www.tchain.com/otoneurology/disorders/bppv/bppv.html http://www.emedicinehealth.com/vertigo/article_em.htm
You can look up here for vertigo tests: http://www.tchain.com/otoneurology/testing/engrot.html
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