"Sinus Infection"

Today I went to school even though I felt terrible. By the end of the day, I just layed on the floor in Mrs. Myers's classroom the whole period. After school, I drove home instead of stay in town like I usually would when I don't have to go to work, so my parents were surprised to see me. I told them I felt sick, so my dad took me to the doctor. The doctor looked me over for less than a minute (literally) and told me I had a sinus infection. It seems to me that, quite often, I end up going back to the doctor so that he can tell me that they were wrong about it being a sinus infection, and that it's the flu or some other unpleasant illness. This is the worst "sinus infection" I've ever had, but I'm not the doctor, right?