If you don't know anything about portion sizes how do you know that you are eating 1500 calories a day?
Also, I think you can eat snacks and still eat 1500 calories.
I average between 1200 and 1300 calories a day and have a couple of snacks. I just don't have meals that are very large.
For breakfast, add some protein and you can may find that you don't get as hungry so quickly.