I have also had bad headaches but no other symptoms. I think mine is just allergies.
Also check out on google 'What On earth are they Spraying"
you might have caught a flu, something viral.
do Complete Blood Count + Sed. rate.
did you try Ibuprofen or other pain killers for the headache?
I get something similar though your sounds worse ..I have put mine down to environmental allergies caused by the aerial spraying they are doing in most states ..do some research, you can ask for a heavy metal toxicity test ..good luck go to Aircrap.org