Otrivin is dangerous and harmful in the long run. It has tremendous abuse /addiction potential and can cause irreversible changes to the nasal mucosal lining. You will need to stop it immediately.
You could be having hypertrophied turbinates, a deviated nasal septum, polyp in the nose. Please consult online for diagnosing your problem.
Next Steps
Steam inhalation twice a day. saline nasal spray use.