hi, I went through your post, what I feel is you must be having congestion in your nostrils due to that there must congestion in sinuses also because which you are sensing bad smell, if tests were required means ENT specialist would have suggested so need of any tests continue to use medicines prescribed by the ENT specialist. you should practice pranayamaa to avoid this problem including sneezing, as pranayamaa will keep your airway clean and healthy. Wish you a speedy recovery.