Wow. I'm sorry to hear of the problems some of you have had, but happy you are on a road to what is hopefully better health. I feel pretty fortunate that I didn't face the same issues.
Mine weren't all that bad. They got weird sometimes but it was nothing like any of my "quit" attempts. But I'd hazard folks such as yourself are the minority. It's a big change. You leave behind literally thousands of chemicals and stop inhaling smoke (which is bad in general). And I dunno it's "withdrawal" per se. Call it an "adjustment". An adjustment to a big change...