After dinner and the masquerade, I felt a more congested and a bit lightheaded, so I went looking for a place to rest a while. Once starmalachite got a look at me and felt my temperature, she insisted that the EMTs have a look. There was no sign of it being anything worse than a nasty sinus-infection flareup (she had a bad cold last week; I seem to have gotten it worse), and everything tested normal except my blood pressure being a bit high (not surprising under the circumstances; she was clearly worried and I was still thinking clearly enough to realize that the situation just might be worse that it seemed). I was starting to feel better, but she convinced me it was probably best to head back to our hotel.
I'm feeling better now, and the fever is broken, so I'll be back at the con. I may decide to take a sick day tomorrow to fully recover, though.