stop biting my nails

I begun biting at age 6, today im 23.
My fingers are weirder than E.T’s fingers.
I always have clenched fists in public, and when alone i end up with my fingers in my mouth.
I dont remember how i started, and dont know how i should quit.
Tried all different nailpolishes, band aids etc.
I have a third of a CM of nail left, and if it wasnt so nasty looking i wouldnt care,
I dont even have pain when i bite because its been exposed for so long.
I do hope to stop, and thought i try to motivate myself in a forum where others have similar challenges,.
so if anyone really believes they have a suggestion for how to bite less, or better yet how to quit. please feel free to advice.
Thank you