Why am I always hungry?

I am having problems with my appetite. It seems that no matter how much I eat during the day, I feel like I didn't eat enough and that I'm still hungry. I can never get full even if eating a whole plate of food. I eat three nutritious meals a day as well as one or two snacks between meals. I have a very health lifestyle: physical activity, plenty of sleep, hydration, etc. Protein, vegetables, and healthy carbs are part of my diet. So I don't understand what's causing me to want to eat more food?

I find that it's so hard for me to ENJOY food whether it's my mother's delicious cooking, or when I go out to eat at a restaurant. Everyone else in my family gets full quickly and I'm embaressed to take seconds to avoid getting made fun of by my family. In fact, my father has made fun of me in the past for wanting to eat more. He called me an "eating machine" and it hurt my feelings.

This is really stressing me out and I really need to know how I can fix this