sore throat and sinus drainage

I have had a sore throat for almost two months. The doc checked for strep. She told me it was sinus drainage and had me take
Xyzel (?). That didn't work. She put me on amoxicillin and a nasal spray. That didn't work. Then she had me on another antibiotic - Avelox. I just finished that yesterday and I still have my sore throat. She keeps telling me that it is the drainage that is causing it. What can I take to thin the mucous (spelling?)? It is driving me nuts. I feel pretty good otherwise and now I am starting to worry that it is something more than drainage. Should I see an ENT?

Thank you for considering my question.

G. Marsh :