If i shut my wrist in a car door, like if i slam the door shut on it, will it break?

Yes I would imagine it is possible to break her wrist if you were to slam a car door on it. The rest is comprised of your forearm bones as well as small bones that are within the wrist itself. The crush injury from a car door could cause significant damage.

I'm very concerned that you have thoughts about harming yourself. You may be the same individual who inquired about vertically cutting over a vein. If I am correct I urge you to seek help from a mental health professional urgently. If you don't have a physician who could refer you, contact a social worker at your local hospital who will help you with a referral.