The doctor diagnosed a sinus infection, and you are correct, antibiotics aren't very effective for this type, according to recent studies, but give it a chance. If that doesn't work, a sinus flush is effective against infections of the upper sinuses, where regular saline irrigation doesn't work due to gravity
http://www.medhelp.org/user_journals/show/2322
The Flip-Turn Sinus Flush 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, or you can kneel down and lean over a bathtub, or perhaps a plastic basin or tub, with the shower running for steam.