What if you ate 3 meals a day and you are still not full. Is that bad a thing. Because I don't want to over eat.?

I know the feeling. I don't EVER remember feeling full. I have to write down what and how much I eat every day to keep from over eating. Good luck.

Depends on the size of the meals, of course.  3 meals of 300 calories each is not much.  But it can also be what you are eating.  If you are leaving something out, your body might need it badly but can only tell you that it is hungry (not hungry for what)