If it is BPPV, it is treatable by a simple manoeuvre, (called the Epley manoeuvre), usually performed by a physiotherapist. The text below is straight from Wiki, but my sister suffered for ages with symptoms similar to yours until she had this done, which cured it in hours (been repeated 18 months later when it came back, but this manoeuvre sorted it out again)
”””””””””””””””””””””
The Epley manoeuvre or repositioning maneuver is a maneuver used by medical professionals to treat one common cause of vertigo, benign paroxysmal positional vertigo (BPPV), of the posterior or anterior canals of the ear. It works by allowing free-floating particles from the affected semicircular canal to be relocated, using gravity, back into the utricle, where they can no longer stimulate the cupula, therefore relieving the patient of bothersome vertigo. This maneuver was developed by Dr. John Epley and first described in 1980.