Update - Got the doctor who gave me the strep test that came back negative - I think she thinks I'm a hypochondriac. She agreed to do another one, but suggested it was just a coincidence that I felt better while I was taking the antibiotics. When I asked if there was anything other than strep that could account for the symptoms, she said it could be allergies, so I got some over-the-counter antihistamines on the way home, and we'll see how that goes. At least I only had to wait about ten minutes to see her.