Where does mucus come from? See below for more details?

I have had this stupid sinus infection, seen the doctor, who gave me penicillan,charged me and arm and leg to tell me what I already knew I had , it has been over 8 days & I still have mucus coming out of my nose and throat. I take vitamins daily and eat healthy. I stay away from people who have been sick, and use sanitizer products all the time.( I hate germs or anything else I may pick up from every day use of door knobs , grocery carts, ect...) Why hasn't this medication cleared this up by now? I'm aware of my mucus membranes and their locations, but how much longer can this still go on?