Why Are My Eyes Watering In My Bedroom?

This has happened for as long as I can remember since I forced to move in there, and yet I haven't really noticed until maybe a couple days ago.  Oftentimes, as I lay in bed, my eyes start to water.  It eventually stops, but some times it lasts a lot longer than other times.

Why is that?  I have no idea, but I should investigate more.  It shouldn't happen, right?  It might have something to do with the room, like the paint.  Or, it might have something to do with the air, whether it's the vents in my room or the central air itself.  Or, maybe it's radon?  The city has radon detectors.  It's weird in that it appears to be a longitudinal study of a kind: You set it up somewhere in your house and you just leave it for, like, three months.  It's free, so maybe I should do it?