Post nasal discharge is one of the reason. How is the sleep pattern and any stress / acidity. Rinse your mouth with water after using the spray..u may be using the spray in a wrong way.
Next Steps
Visit a local ENT specialist or you can do teleconsultation.
Health Tips
Avoid the tendency to clear the throat repeatedly..Take steam inhalation with mouth closed & deep breathing from nose.
Avoid too hot & too cold water..avoid spicy/ sour/ coloured food.