Character constantly Bouncing issue

so im fairly new to scripting and working with unity in general. i have written a script for basic movement of my character, but when i press play in unity to test it out it bounces. i had it working just yesterday. anyways i want to make it so i push to jump not a constant jumping loop like it is i may have a setting or something on that im not familiar. anyways here is the script for it

using UnityEngine; using System.Collections;

public class movement : MonoBehaviour { //Variables public float speed = 6.0F; public float jumpSpeed = 8.0F; public float gravity = 20.0F; private Vector3 moveDirection = Vector3.zero;

 void Update() 
 {
 CharacterController controller = GetComponent<CharacterController>();
 // is the controller on the ground?
 if (controller.isGrounded) {
                     //Feed moveDirection with input.
                     moveDirection = new Vector3 (Input.GetAxis ("Horizontal"), 0, Input.GetAxis ("Vertical"));
                     moveDirection = transform.TransformDirection (moveDirection);
                     //Multiply it by speed.
                     moveDirection *= speed;
                     //Jumping
                     if (Input.GetButton ("Jump"));
                     moveDirection.y = jumpSpeed;
     
             }
 //Applying gravity to the controller
 moveDirection.y -= gravity * Time.deltaTime;
 //Making the character move
 controller.Move(moveDirection * Time.deltaTime);