As I suspected, I've got a sinus infection. The PA gave me a prescription for Augmentin (amoxicilin/clavulanic acid) and a decongestant/expectorant (phenylephirine/guaifenisin).
I still need to make an appointment with my eye doctor. My eye, which had been doing well for the past couple months, has begun bothering me again (though it's nowhere near as bad as it was last year). He's probably going to put me on low dose doxycycline for 3-4 months again. Ick.