The way your body reacts to hunger is your stomach senses that it's empty or getting empty and then your stomach sends signals to your brain which start with hunger pains, stomach growling etc.
Your brain then tells you that you need something to eat and when your stomach is full the stomach sends signals to your brain that you're not longer hungry.
Hunger in the body is partly controlled by a part of your brain called the hypothalamus, your blood sugar (glucose) level, how empty your stomach and intestines are, and certain hormone levels in your body.
If you are still constantly hungry after eating you could be getting diabetes or you may also have Leptin Resistance.
My sister was always hungry after eating and she got tested and was on the borderline of being diabetic so you should see a doctor about it and get tested.
Diabetes can be deadly if not treated in time so always get tested just to be safe.
Feeling hungry constantly even after eating is not normal and you should see a doctor about it.
You could have what's known as a Leptin Resistance.
Leptin is a hormone that is produced by your body fat that controls whether or not your stomach feels full after eating.
You may also have Hyperthyroidism which is a condition that is characterized by an overactive thyroid which can also cause you to have a constant hungry feeling.
So you should certainly get checked out by a doctor especially if you're always feeling hungry even after eating.