why player jumps forever

I have been watching the 2D Character Controllers tutorial. I set up everything like he did using my own sprites. I ran into a problem when adding jump. He adds a game object to detect ground which worked okay at first. I got the check mark when on the ground and when I fell, it went away. So I tried setting up jump with a blend tree to smooth animation. When I did this, some how player no longer detected the ground. Player would also jump with out me hitting space bar. He would also jump forever. So I changed the code and just made the animation normal. After that everything worked fine. This was at midnight last night. Saved closed everything and went to bed. When I got up everything I did was still the same. But When I hit play the player jumps again without hitting space bar forever. very strange and frustrating any help would be appreciated.

 using UnityEngine;
 using System.Collections;
 
 public class PlayerControl : MonoBehaviour 
 {
     public float jumpforce =700f;
     public float maxSpeed = 10f;
     bool faceRight = true;
 
     Animator anim;
 
 
 
     // Use this for initialization
     void Start () 
     {
         anim = GetComponent<Animator> ();
     
     }
     
     // Update is called once per frame
     void FixedUpdate () 
     {
 
 
         anim.SetFloat ("vSpeed", rigidbody2D.velocity.y);
 
 
 
         float move = Input.GetAxis ("Horizontal");
 
         anim.SetFloat ("speed", Mathf.Abs (move));
 
         rigidbody2D.velocity = new Vector2 (move * maxSpeed, rigidbody2D.velocity.y);
 
         if (move > 0 && ! faceRight)
                         flip ();
                 else if (move < 0 && faceRight)
                         flip ();
     
     }
 
        void Update()
     {
         if( Input.GetKeyDown(KeyCode.Space));
         {
 
             rigidbody2D.AddForce(new Vector2( 0, jumpforce));
         }
     }
 
     void flip ()
     {
         faceRight = !faceRight;
         Vector3 theScale = transform.localScale;
         theScale.x *= -1;
         transform.localScale = theScale;
 
     }
 
 }