Yes, it does seem unusual for a 16 year old to have such severe dizziness that he has to lie down and for it to last for a day.
There are many different causes of dizziness.
Basically, the causes are divided into two, Peripheral and Central.
Peripheral causes are causes in the ear, like BPPV, labyrinthitis, vestibular weakness, etc.
Central causes are causes due to other conditions like cerebellar conditions, strokes, etc. Systemic conditions like low BP, infections, disease conditions, etc. can also cause dizziness.
You should show your doctor for this. A number of investigations need to be done to find the cause of your dizziness. Once the exact cause of dizziness is found, it can be treated.
You can look up here:
http://www.mayoclinic.com/health/dizziness/DS00435/DSECTION=causes http://www.wisegeek.com/what-causes-dizziness.htm You can look up here for vertigo tests:
http://www.tchain.com/otoneurology/testing/engrot.html You can look up here for exercises:
http://www.drarmstrongmd.com/vestibularexercises.doc http://www.tchain.com/otoneurology/treatment/rehab.html I hope my answer has helped you. Please click on the green 'accept' button below for accepting this answer. Feedback/Bonus will be appreciated.