I read your question carefully and I understand your concern. As you yourself said there can be several causes for nausea and vertigo (reeling sensation). It would have been useful if you had added some more info on your age and other possible medical issues. Anyway, usually by far the most common cause is an ear related issue. As for what to do of course the first step will be physical examination to look for hearing, eye movement or nystagmus, neurological signs which might indicate MS or an acoustic neuroma. If there is suspicion of a neurological cause a MRI might be the initial exam. If there are no such signs and a ear related cause is confirmed to be the primary hypothesis then at times other exams like audiometry or nystagmography may be done to identify the type and site of damage (not necessarily though if the cause is clear). As for the treatment that depends on the cause which the exams will reveal, can not be determined so far ahead. I hope things work out for the best.