Creating only one joint

Hi guys i have script that creates joint on collision with another rigidbody ,but the problem is that on collision it creates multiple joints im not sure why, but i think its because the charachter have many childs
here is my script

 using UnityEngine;
 using System.Collections;
 
 [DisallowMultipleComponent]
 public class StickyObject : MonoBehaviour
 {
     void OnCollisionEnter(Collision c)
     {
         var joint = gameObject.AddComponent<FixedJoint>();
         joint.connectedBody = c.rigidbody;
     }
 }

i tryed [DisallowMultipleComponent] but its not working on runtime i want it to create only one joint because i have destroy script which destroy the joint on click but when it creates multiple joints its not working anyone got any ideas how i can do this? Thank you