Not normal. What your are describing is not normal. This could be related to a chronic sinus infection. Less likely, but something that has got to be considered is a tumor of the nasal cavity/olfactory groove. Please get check by your local ent. At a minimum, you will need an endoscopy of the nasal cavities and a ct of the sinuses.
Hyposmia. The sensation of smell is the result of stimulation of the olfactory nerve (nerve of smell) in the upper third of the nasal lining. This is a nerve that arises from the front of the brain. Alteration of the sense of smell is extremely complicated but can arise from disease of the upper nose such as infection of the nose or from the sinuses. It can result from migraine. See an ENT doctor.