WiFi uses microwaves in the 2.4GHz, and also the 5GHz frequency bands. You may have noticed that microwave ovens have a well bonded metal case surounding them, and you can only view the innards cooking via the glass door which has a perforated metal screen over it. In the same way that microwaves can excite water molecules which heats them up, so they can your brain! Albeit WiFi equipment doesn't (usually!) transmit anything like the same RF power as a microwave oven, sustained close proximity to an AP could well give you a headache.
I remember once observing a demonstration of an amateur television transmitter running about 25W in the 430MHz band, which of course is well below 2.4GHz. I was probably about 25ft away from the antenna, but each time the transmitter was keyed I felt an unusual sensation in my head. The guy running the station wouldn't believe me until I was blindfolded and was still able to tell him precisely when he keyed up the transmitter and when he turned it off!!
I suggest you get yourself distanced from it a little, and perhaps don't do any more 3 hour sessions without a break...
ROGER - G0AOZ.
