There are no over the counter supplements that have been proven safe and effective to curb hunger. You may want to talk to your doctor about it - there are several hormones, generally associated with hunger, that may be affecting your appetite. Unfortunately, many of them have no diagnostic test (such as GLP-1) nor a therapeutic replacement. My previous company has intellectual property rights to Leptin, and no one has yet developed a product the FDA has found worthy of approving to help against weight loss.
In fact, there was an LA Times story earlier today about hormones such as leptin that may determine your success in the battle against weight:
http://www.latimes.com/health/boostershots/la-heb-diet-ho...
However, there's a lot of research showing that behavior modification can be helpful. There are a few tricks.
1. Drinking a glass of water before eating will make you feel fuller.
2. Making sure each serving has greater than 5 grams of fiber will help you feel fuller and block the absorption of some of the carbohydrates
3. It takes the brain 20 minutes to feel full after eating - slow down, and you'll likely eat less
Even Rx products are not without risk. Phentermine is a stimulant, Meridia was just linked to cardiovascular issues (though it's been known for a long time there was the possibility) and Xenical has had some issues with liver toxicity.
Remember that serving sizes differ based upon the food. So, a serving of plain Cheerios gives you a lot more food than a serving of Frosted Flakes. Avoid sodium which can lead to water retention, keep fats and sugars in check, and think about seeing a dietician who can help you come-up with a reasonable plan for losing the weight in a healthy, productive way.
But, I'd really encourage you to talk to your doctor as well to see if it may be hormone related that you're not feeling any satiety during the day as it may be a hormonal issue you realistically can not control.