I had EXACTLY the same problem few years ago. I don't even remember when and how it stopped. All I remember is that I thought -- without any professional medical consultations -- it was a matter of acquiring better oral hygiene. Hence, I did a thorough dental cleaning, and increased the frequency of brushing, gargling with Listerine, etc.

I have this seriously unstoppable habit of biting my inner lips and cheeks too. The Docs: How damaging can that be? How to stop?