Objects clipping

Hello everybody! I have a problem with physics (I think). I am new in unity, so I don't know how to solve it, and I was searching for some answers in google and found nothing. Basicly, my character clip through walls, doors, and everything when I walk towards the object. This is what happens (youtube.com). What could it be?

This is the code I use:

Code (CSharp):

1.  
2.     [SerializeField] float speed = 8f;
3.  
4.     //Private variables
5.     Rigidbody rb;
6.     float xDir;
7.     float yDir;
8.     void Start() {
9.         //Get the component rigidbody
10.         rb = GetComponent<Rigidbody>();
11.     }
12.  
13.     void Update() {
14.         //Update variables
15.         xDir = 0f;
16.         yDir = 0f;
17.         //Get input
18.         if (Input.GetKey(KeyCode.W)) {yDir = 1f;}
19.         if (Input.GetKey(KeyCode.S)) {yDir = -1f;}
20.         if (Input.GetKey(KeyCode.D)) {xDir = 1f;}
21.         if (Input.GetKey(KeyCode.A)) {xDir = -1f;}
22.         //Fix diagonals
23.         if (xDir != 0 && yDir != 0) {
24.             xDir *= Mathf.Cos(Mathf.PI/4);
25.             yDir *= Mathf.Cos(Mathf.PI/4);
26.         }
27.     }
28.  
29.     void FixedUpdate() {
30.         //Move the player
31.         Vector3 move = new Vector3(xDir, 0, yDir);
32.         rb.MovePosition(transform.position + move * speed * Time.deltaTime);
33.     }