You keeping your meals relatively small? If you stuff yourself, you won't be hungry to eat in a couple hours.
Gradually get your body used to eating frequently. Start out with meals every 3 1/2 hours. After a few days, go 3 hours. Then down to 2 1/2. In a little while, you should be eating every 2 hours or so.
Take Blood's advice, too. That's a nice and easy way to get more calories.
~dE