I get the mid-morning and mid-afternoon hunger?

what can I eat that will help me feel full without adding too many calories? I go to the gym in the morning - eat a huge bowl of cereal with fruit and a gl of OJ after that then head into work. I eat lunch around 1230 - usually a salad with lots of chicken.... but I'm always starving around 4 or so in the afternoon. My problem is I get sick to my stomach and a horrible headache when I get too hungry. Drinking water doesn't help because I drink a ton already and I eat cups of ice throughout the day.