So, it turns out it was a full blown migraine, which acetaminophen does jack shit for. It only dulled the pain as long as I laid perfectly still, but the pressure was so bad I would become dizzy, lightheaded, and nauseous at the slightest twitch; I couldn't even fall asleep because simply entering a dream would trigger it. I finally caved and took the ibuprofen, and after about thirty minutes, everything dulled down so I could comfortably sleep; I felt much better when I woke, though I've had persistent, very dull pressure in my left temple all day.
I think I need something that's anti-inflammatory (to combat the pressure as well as the pain), which acetaminophen is not.