I'd love to see some responses for this too...
Unfortunately, I'm not going to be of any help re: an answer to your problem, but I've been feeling MUCH the same way. I used to not have as big a problem with cutting down on my portions and I haven't made any drastic changes, just smaller portions, more veggies/fruits, less refined foods so I don't get it either. I'm also getting headaches and a constant feeling of hunger. Boo.
I guess the only comfort I can offer is you're not alone?