[Schrodinger's Cat]

My girl friend went through symptoms much like yours, LJ. She'd get paranoid if she smoked weed (didn't smoke it often though - the symptoms made her smoke it even less), and she'd get episodes where she felt that she literally couldn't breathe. Once I took her down to the ER it was so bad, and they came up with zilch. She was going through a very stressful time - her defense of her doctoral thesis was coming up and she and her grad advisor were really at odds over one segment of her paper. She reached the point where she was coming home and belting down a couple of shots of Cuervo every night, just to feel like she was breathing normally again.

Long story short, a doctor finally figured out she was hypoglycemic and she cut way back on sugar and caffeine. She also learned some simple breathing/relaxation techniques, and ultimately passed her oral defense with flying colors. She says her symptoms now have almost completely vanished.

So could be stress and a bit too much of them funny lookin' cigarettes and too many snickers bars. Simple as that.

I wouldn't fool around though if your symptoms continue. Find a really good doc and do the full array of tests just to make sure.