Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concern.. As per your complain the symptoms of clogged stuffy feeling of nose along with bad breath and bad smell from nose can be due to Sinusitis or sinus infection.. Other causes can be oral infections, upper respiratory tract infection, acid reflux etc.. I would suggest you to consult an Otolryngologist and get evaluated and he can advise yo investigations like PNS View of x ray, nasal endoscopy and a clinical examination of nose, oral cavity and thoat to rule out the exact cause of problem and treatment can be planned accordingly.. As of now you can start doing steam inhalations with a few drops of Eucalyptus oil in boiling water.. You can also chew flavoured sugarfree chewing gums and gargle with flavoured antiseptic mouthwash. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora..