Move player backwards when firing a gun. Unity 2D. Top Down

I used the AddForce method, and the idea was to basically take the mouse position and store it in a variable lookDir, then to make an addforce with -lookDir but it turned out very wonky and it didn't work very well, there's the recoil and most of the time it goes to the right direction but sometimes it doesn't and sometimes the recoil is too strong. Here's the code:

using System.Collections; using UnityEngine;

public class PlayerShoot : MonoBehaviour { [Header("Gun Pointing")] public float offset; public bool isFacingLeft; public Vector2 lookDir;

 [Header("Gun Shoot")]
 public float timeBeforeShooting;
 public float reloadTime;
 public float timer;
 public float recoilForce;
 public int maxAmountBullet = 8;
 public int bulletsAmount;
 public GameObject bullet;
 public Transform shootPoint;
 public Rigidbody2D rb;

 [Header("Reload")]
 public bool canShoot;
 public bool isReloading;

 private void Start()
 {
     bulletsAmount = maxAmountBullet;
 }

 private void Update()
 {
     GunDirection();

     timer += Time.deltaTime;

     if(bulletsAmount == 0)
     {
         canShoot = false;
     }
     else if(bulletsAmount > 0 && !isReloading)
     {
         canShoot = true;
     }

     if (Input.GetButtonDown("Fire1") && canShoot && bulletsAmount > 0 && timer > timeBeforeShooting)
     {
         Shoot();

         bulletsAmount--;
         timer = 0;
     }

     if(Input.GetKeyDown(KeyCode.R) && !isReloading && bulletsAmount < maxAmountBullet)
     {
         StartCoroutine(Reload());
     }
 }

 private void GunDirection()
 {
     Vector3 difference = Camera.main.ScreenToWorldPoint(Input.mousePosition) - transform.position;
     float rotZ = Mathf.Atan2(difference.y, difference.x) * Mathf.Rad2Deg;
     transform.rotation = Quaternion.Euler(0f, 0f, rotZ + offset);
     //Direction of the mouse
     lookDir = Camera.main.ScreenToWorldPoint(Input.mousePosition);

     if (rotZ > 90 || rotZ < -90)
     {
         isFacingLeft = true;
     }
     else
     {
         isFacingLeft = false;
     }

     if (isFacingLeft)
     {
         gameObject.GetComponent<SpriteRenderer>().flipY = true;
     }
     else
     {
         gameObject.GetComponent<SpriteRenderer>().flipY = false;
     }
 }

 private void Shoot()
 {
     Instantiate(bullet, shootPoint.position, transform.rotation);

     rb.AddForce(-lookDir * recoilForce, ForceMode2D.Impulse);
 }

 private IEnumerator Reload()
 {
     canShoot = false;
     isReloading = true;

     yield return new WaitForSeconds(reloadTime);
     bulletsAmount = maxAmountBullet;

     canShoot = true;
     isReloading = false;
 }

}