Trying to add 45deg strafing to my Character Controller.

Below is my Character Controller script. Currently the character rotates towards the mouse and I can move it using WASD in relation to the mouse position. (ie. W moves the character towards the mouse, S moves character away from mouse). I can strafe left and right along the players X axis, however I can't seem to get it to move forward/backwards as well as left/right. Essentially I have no 45deg angles. Let me know if you need anymore information.

 using UnityEngine;
 
 public class PlayerController03 : MonoBehaviour
 {
     public float rotateSpeed = 0.2f;
     public float walkSpeed = 3f;
     public float walkBackwardsSpeed = 2f;
     public float runSpeed = 6f;
     public float speedSmoothTime = 0.1f;
     public float gravity = -12f;
     public float jumpHeight = 1f;
 
     Animator animator;
     Camera cam;
     CharacterController controller;
 
     private Vector2 input;
     private Vector2 inputDir;
 
     bool aiming;
     bool running;
     float currentSpeed;
     float speedSmoothVelocity; 
     Vector3 velocity;
     float velocityY = 0f;
   
     void Start()
     {
         controller = GetComponentInChildren<CharacterController>();
         animator = GetComponentInChildren<Animator>();
         cam = Camera.main;
     }
 
     void Update()
     {
         //maps raw input to normalized vector2
         input = new Vector2(Input.GetAxisRaw("Horizontal"), Input.GetAxisRaw("Vertical"));
         inputDir = input.normalized;
 
         //Grabs aiming and running 
         aiming = Input.GetMouseButton(1);
         running = Input.GetKey(KeyCode.LeftShift);
 
         //gets the current speed of the player depending on whether they're running or walking and dampens
         float targetSpeed = ((running) ? runSpeed : walkSpeed) * inputDir.magnitude;
         currentSpeed = Mathf.SmoothDamp(currentSpeed, targetSpeed, ref speedSmoothVelocity, speedSmoothTime);
 
         //activates aiming animation
         if(aiming){ 
             animator.SetBool("isAiming", true);
         }else{
             animator.SetBool("isAiming", false);
         }
 
         if(Input.GetKey(KeyCode.Space)){
             Jump();
         }
 
         //creates a ray to the current mouse position and rotates the player towards it
         Ray ray = cam.ScreenPointToRay(Input.mousePosition);
         int layer_mask = LayerMask.GetMask("Ground");
         RaycastHit hit;
         if(Physics.Raycast(ray, out hit, 100, layer_mask)){
             Vector3 targetDir = hit.point - transform.position;
             Vector3 newDir = Vector3.RotateTowards(transform.forward, targetDir, rotateSpeed, 0.0f);
             if(inputDir != Vector2.zero || aiming)
                 transform.rotation = Quaternion.LookRotation(new Vector3(newDir.x, 0, newDir.z));
         }
         
         //sets the initial velocity, but this is when the player is standing still, but allows to jump in place
         velocity = transform.forward * currentSpeed + Vector3.up * velocityY;
         //sets the velocity of the player based on input
         
         if(inputDir == Vector2.up)
             velocity = transform.forward * currentSpeed + Vector3.up * velocityY;
         if(inputDir == Vector2.down)
             velocity = -transform.forward * currentSpeed + Vector3.up * velocityY;
         if(inputDir == Vector2.right)
             velocity = transform.right * currentSpeed + Vector3.up * velocityY;
         if(inputDir == Vector2.left)
             velocity = -transform.right * currentSpeed + Vector3.up * velocityY;
         if(inputDir == Vector2.zero){
             velocity = Vector3.Lerp(velocity, Vector3.zero, speedSmoothTime);
         }
         // Debug.Log(velocity);
     }
 
     void FixedUpdate(){
         Debug.Log(velocity);
         controller.Move(velocity * Time.deltaTime);
         currentSpeed = new Vector2(controller.velocity.x, controller.velocity.z).magnitude;
         velocityY += Time.deltaTime * gravity;
         if(controller.isGrounded){
             velocityY = 0;
         }
     }
 
     void Jump(){
         if(controller.isGrounded){
             float jumpVelocity = Mathf.Sqrt(-2*gravity * jumpHeight);
             velocityY = jumpVelocity;
         }
     }
 }