What Causes Sinus Infection, Dry Cough, Mucus, Head And Back Pain?

hi, i was wondering if you could tell me what you think i might have... i was diagnosed with a severe sinus infection, but i have a dry cough that has been persistant for 3 1/2 weeks now... it kills my head whenever i cough also, it is beginning to hurt my lower back... no fever.. sometimes mucus.. runny nose.