Hello, I went through your question And understand your concern.
I think you are expierencing benign paroxysmal positional
vertigo. This situation, unlike viral infections of the
vestibular nerve, tends to last shorter and have recurrences. That's why your gp prescribed betahystine.
You can have a
neurologist perform you the Epley manouver, which should resolve the
dizziness.
If it does not help, and given the not usual frequency (3 ep in 10 months) I would reccomend an
MRI, which would exclude other causes(including viral infection of the vestibular nerve) rather than make the diagnosis of BPPV.
Betahystine has several adverse effects like all drugs. But some reports have shown benefitial effect on BBVP. So it is not entirely safe, but if you have for sure BBVP I would reccomend to continie this therapy.
Wishing you good health, please feel free for further questions.