I had the same habit of biting my lower lip, I will tell you what I did to get rid of it. I started chewing the gum, all the time. In the beginning this use to give me headache, constant chewing, than it became a habit as biting lower lip was. There is another thing you can do, start noticing your activity for a week and whenever you note yourself biting the lip, try to ask question from yourself that why are you doing it?. This question and answer will help you getting rid of this unconscious habit.
