Talk to Ent Specialist on Mucus In Throat

There something in my throat all time, (thick, whitesh, transparent mucus or whatever), but it's always there in morning in evening day night from last 4/years. Doctor's said this is happening because of allergy but after taking allergy dots/medicine result was 0% so doctor told me it's not happening because of allergy so i want to know if it's not because of allergy then where the problem is by the-way my endoscopy was clear so no GERD/Dyspepsia.