I worked in a family practice for many years and we had so many parents come in with the same concern. Your doctor was right, kids do go through this stages, we as parents hate it, but soon you will see that you child will start eating well. Something that really helped a lot of parents that I got to know was having a family meal together. Avoid treats or snacks between a meal. If he begs, simply say that you're out of that particual item. As bad as it may sound, you have to let the hunger build up, and then bring out something with a yummy smell that would be hard to resist, like roasted chicken. Following those steps you can start introducing new foods.