It's normal. You go through the pink cloud phase where you're just like "OMG I can't believe I didn't quit smoking years ago this is so easy and wonderful," but inevitably your body readjusts and then it's like, "Oh, yeah, right, I'm technically a drug addict."
Smoking is a very difficult habit to break. If you've been just going cold-turkey now might be a good time to look into maybe some support groups. Or picking up a new, healthier habit... exercise is a good one to help with the food cravings and moderate exercise is usually fine for pregnant women, though talk to your doctor about it. Or just doing something mildly pleasurable! Every damn cigarette you don't smoke is a victory and a little reward can be nice:)