Is the chronic sinus infection only 3 months. Did you have episodes before. It does reduce in severity with medications means the infection is persistent. Do you have any nasal allergy. If you have taken 1-2 courses of antibiotics and still symptomatic then you need a scan to check state of sinuses before trying to change the diagnosis.
Next Steps
If you have met ENT , review back ,or else meet an ENT specialist and then you might require CT scan of nose and sinuses
Health Tips
1. Continue stem inhalation
2. Continue sprays till getting a scan or an