This question needs an honest answer.
Is the cannabis you are smoking imported by any chance?
I smoke nothing but stuff i grow , or stuff that comes from one of our fourty Medical Cannabis Clubs, here in San Francisco. Never an after smoking ill feeling.
On the other hand.....if you are smoking imported weed you could be inhaling substances used to help conceal odor for smuggling purposes, and or, older weed that may have a mildew or mold on it that isnt visable to the eye.
Just a thought. I hope you get feeling better.

dai*ma