Hmm... youre probably just a 'lightweight' as theyre called. Nothing wrong with that, its a good thing actually - just means it takes less Herb to get you high. How long have you been smoking for and how often do you smoke? Its either that youre a lightweight, or you just have a naturally low tolerance to the Herb. Nowt wrong with either of those mate. Me, I can smoke quite a bit and not pass out or throw up, but I have been smoking a couple of times a month for about 4 years now. Your body just gets used to it.
Another thing you mentioned was blunts. They are VERY high in nicotine and tar, so it could be that thats making you feel unwell. Try getting some small rizlas (blues are the best I reckon), and roll a small pure spliff. Dont add any tobacco unless you smoke cigs already, and stay away from the grav bongs until your tolerance builds up a little. Ive heard that those things FUCK YOU UP, although Ive never been arsed to try one myself.