For prolonged sinusitis with headache and neck pain, you can use over-the-counter pain relievers like acetaminophen or ibuprofen to reduce pain and inflammation. Saline nasal rinses can help clear nasal passages, and a generic oral decongestant like pseudoephedrine may relieve sinus pressure. However, because your symptoms are prolonged and accompanied by neck pain, it is highly recommended to consult a doctor. You may require targeted prescription treatments, such as nasal steroid sprays (like fluticasone) or antibiotics (like amoxicillin) if a bacterial infection is suspected, to help you recover safely and quickly.