got char stuck near objects.

i am trying to make this character hit some boxes but when he hits, the boxes can push him over or backwards

` var speed : float;
var speedincrease : float;
var massa : float;
private var motor : CharacterMotor;
var posy : float;

function Start () {
 posy = transform.rotation.y;}

function Awake () {
motor = GetComponent(CharacterMotor);}
function Update () {
    motor.inputJump = Input.GetButton("Jump");
	transform.position.x = transform.position.x+Time.deltaTime*(speed-massa);
	transform.position.z = 0;
	transform.rotation.y = posy;}			`

Increase the mass of the character and check the mass of the box. Keep the real world mass to get better result