Headaches from smoking?

I’ve been smoking for about two years now (there were phases where I quit and then started back up again)... But lately, over the last two or three weeks, I’ve been getting these unbelievable headaches after just a single Marlboro Red... It's unreal. Before this, I could smoke a whole pack a day without feeling anything at all. What could be causing this? Is this serious? My head hurts so much that I actually start to feel dizzy...

Nicotine triggers vasoconstriction—basically squeezing those blood vessels shut—which cuts down on oxygen flow. It probably teamed up with a few other culprits that do the same thing, like menopause, atherosclerosis, migraines, high muscle tension, overactive sympathetic nervous system activity, or even just the cold causing vessels to constrict.