Had sinus infection for 18 days, took full 10 day antibiotics, a bit better but not completely, what should i do next so it will go away completely?

Sinusitis: What makes you think you had sinus infection instead of sinusitis or sinus inflammation? what were your symptoms? do you have a history of nasal congestion, allergies or chronic sinus infection? what else were you treated with? any decongestant or anti-histamines? What antibiotic was prescribed? Not any antibiotic will work on acute vs. chronic sinus infection. Consult an ENT.