Chances are you experienced a lack of oxygen to your bloodstream.

Smoking blunts like that are not good. They feel and sound good, but they are HORRIBLE for you and quite frankly you waste a lot of weed.

The thing is, the paper/tobacco leaf is so thick that it actually has the tendancy to dillute the THC as it reacts in your lungs. Therefor you don't actually get the chance to utilize your cannabis properly. Thus, you are wasting your shit...Oh also, the whole time the thing is burning you're wasting it as well. All that extra smoke going up off the tip of the lit end is wasted smoke...

Also, your lungs cannot absorb all the tobacco leaf content so it basically just starts blocking everything off. It's like taking the paper, melting it, then coating the inside of your lungs with it. This causes that "light headed" feeling.

Too much of this together and you have yourself a lack of oxygen situation that can have moderate to severe affects.

Considering you stated you smoked cigarettes since you were 12, I'd put my money on lack of oxygen to your bloodstream without question.

Try smoking a little less on the intense side.

For instance, I have myself a cheap little glass pipe. I'll pack a bowl, smoke it up real quick then take like a 5-10minute breather. Then if need be I'll pack another bowl and smoke it up. I usually get a MUCH more dramatic and satisfying high than I ever have from a blunt.