Welcome NH, you're not alone.

It has been said, but i just wanted to come in and 2nd that; you're smokin too much at once.
I used to try and take long drags/hits when smokin, to make sure I saturated my lungs with each hit. Before I knew it, I had taken a couple good hits without takin a couple breaths of oxygen only haha...
Then I would get some of the symptoms you're talkin about. I taught myself to take it easy and breathe in between hits, The high will still be there.
-My bro actually passed out once while standing. Wasnt letting enough oxygen get to his brain.