If you are not measuring, you must have a better eye than I do. I have been zoning/paleo since January. I still have trouble eying fruit and fish. I pretty much have the meat down.
If you have never measured you would be surprised at how much you are eating, or not eating. Try it, measure one meal and see how much 1/2 cup of blueberries actually is. Its a small handful, far less than what I originally thought. One tablespoon of almond butter is less than I thought as well.
So give it one day, and see if are really zoning correctly!