You may possibly have a chronic sinus infection of the upper sinuses (frontal and sphenoid) which often do not respond to antibiotics because of low blood supply to the area, or it could be a stubborn virus that you got because of the unusually cool weather in Chicago this summer. You could also possibly have an opportunistic fungal or mold infection up there, along with the bacterial infection.
Read about the cause of chronic here:
http://www.medhelp.org/user_journals/show/2322
You should go to an ENT before trying a Flip-Turn Sinus Flush.
It is mildly risky, because you have to bend over to do it, preferably in a shower, but you can also do it outside on soft ground.