Transform.LookAt stops working after CharacterController.Move is used.

If I don't move my character (A Cube with a CharacterController attached to it) , my rotation script works perfectly, being it looks at the Mouse Cursor. Once i make any movement using CharacterController.Move, it instantly freaks out and stops following the mouse , but still makes small movements when my mouse is moved. Any ideas?

The view is a top down shooter, the "gun" will follow the mouse and point at enemies

 using UnityEngine;
 using System.Collections;
 
 public class PlayerMovement : MonoBehaviour
 {
 
     CharacterController Char;
     public float MoveSpeed = 15;
 
     // Use this for initialization
     void Start()
     {
         Char = this.GetComponent<CharacterController>();
     }
 
     // Update is called once per frame
     void Update()
     {
         float x = 0;
         float z = 0;
 
         if (transform.position.y != 1)
             transform.position = new Vector3(transform.position.x, 1, transform.position.z);
 
         if (Input.GetKey(KeyCode.W))
         {
             z = 1;
         }
         if (Input.GetKey(KeyCode.S))
         {
             z = -1;
         }
         if (Input.GetKey(KeyCode.D))
         {
             x = 1;
         }
         if (Input.GetKey(KeyCode.A))
         {
             x = -1;
         }
         Char.Move((new Vector3(x, 0, z) * Time.deltaTime) * MoveSpeed);
 
         Vector3 mousePos = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, 1));
         transform.LookAt(mousePos, Vector3.up);
 
     }
 }