Collision 2D doesnt work

so, my collision wont work.. i've attached rigidbody2d and collision collisionbox2d to my object

i check the collision using this:

void OnCollisionEnter2D(Collision2D sdd){ Destroy (sdd.gameObject); }

so..the result is.. it will destroy the first game object that contacted with it.. but after that.. it wont work anymore.. very weird result.. and i dont put the script in the update..