I have bitten my nails for my whole life---about 23 years now... I bit them really bad...until they bled, down to the white moon-looking thing. I've tried everything--including those nail polishes(they dint work). I even tried accupuncture and hypnitism...never worked!!
I found this product on-line called "Control-It"...it is the ONLY thing that I am completely disgusted by.
http://www.stopbitingnails.com/
It tastes HORRIBLE!!! It was about $20 for about a months supply----but it lasts WELL over a month(I've been using it for about 3 months now). It comes in this little 1/4 oz. container...it looks small...but it goes a LONG way. It is like a balm-typed cream--that you just dab on your nails. It is the only thing that has helped! My nails look amazing! After your nails start to heal, you'll notice that the skin below your cuticle is starting to get little peels--its natural..it's the skin repairing it self! It works so well. I also got one of those 7-way nail buffers which helped with making the nails look decent, because as your nails grow they are going to be jagged looking-trust me--this stuff works!