I have sever sinus congestion, I have had a Z-pac, as well as 10 days of penicillin, neither did anything. I have been using a nasal decongestant, oxymetazoline. Well over a month now. It works, most days, but some days not so good. Can't breath at night, a mouth breather I become. I think it may be a viral infection, or even a yeast infection. Any suggestions?