Around, 2 weeks ago I had what at that time I thought was the flu, It lasted for waaaaay longer than the flu normally does for me, so I decide to see a doctor.
He goes through the usual list of causes, then he asks me if I own a gas detector.
I go out to home depot and buy one, and it turns out my home has been contaminated with carbon monoxide for about 2 weeks now.
PLEASEbuy one if you do not own one already, carbon-monoxide is completely odorless and can kill you relatively quickly, sometimes with very small symptoms.