Your symptoms suggest chronic sinusitis, possibly with a deviated septum or nasal allergy, which is why you get only temporary relief and depend on sprays. Continue Montelukast + Levocetirizine as prescribed, but avoid overusing nasal decongestant sprays as they can worsen blockage over time. Do regular steam inhalation, saline nasal rinses (like neti or saline spray), and stay away from dust and allergens. Since this has lasted 3 years with one-sided blockage and headache, it?s important to consult an ENT specialist for a detailed check (like nasal endoscopy or CT scan), as you may need long-term treatment or a minor procedure for lasting relief.