Hi, Catherine !
Don't feel badly, during my eating days, I could pack away a small pizza or half a chicken.
Learning portion control takes time. It also takes time for the human stomach to shrink, but as you decrease your portions, you will find that your stomach shrinks too. Like I said, at one time, I could sit down and eat a small pizza. Today, if I tried that, I'd be seriously sick to my stomach.
One thing I would recommend is making sure you're eating foods that are high in FIBER. Foods that have fiber help keep you full for longer. What foods are high in fiber ? Fresh fruits and veggies are high in fiber. Whole grain breads and cereals, beans, legumes, etc. If you can increase the amount of fiber you eat, with time, that will help you feel more sated.
Could you tell us about bit about what you've been eating ? Do you eat 6-9 servings of fresh fruit and veggies ? If not, that's one thing you can do that will help you stay full for longer during the day. Are you drinking enough water ? Some times hunger isn't really hunger, but thirst. So, before you run to the frig, try drinking a BIG glass or two of water.
You can continue to eat pizza, but instead of eating the entire pizza. Have a slice and pair it with a big green leafy salad. This way, you won't feel deprived.
And if you are under stress, you need to find other ways to reduce your stress that don't involve food. You might want to read this great Spark article on emotional eating. You may find it helpful. www.sparkpeople.com/resource/wellness_arti