Player gets slower while jumping

Unity Engine
1

Hey Guys
I use this script to make my player walk automaticly forward and jump if i click… But if i jump again when he grounded he gets slower and slower?
Here is my script:

using UnityEngine;

using System.Collections;



public class runnerscript : MonoBehaviour {
	
	
	
	public float Acceleration = 10;
	
	public float maxSpeed = 15;
	
	public Vector3 jumpVelocity;
	
	
	
	private bool touchGround = false;
	
	
	
	private bool started = false;
	
	
	
	IEnumerator PauseOnStartup() {
		
		yield return new WaitForSeconds(5);
		
		started = true;
		
	}
	
	
	
	void Start() {
		
		StartCoroutine(PauseOnStartup());
		
	}
	
	
	
	void Update () {
		 
		
		
		if (!started) return;
		
		
		
		if (touchGround  Input.GetButtonDown ("Jump")) {
			
			rigidbody.AddRelativeForce (jumpVelocity, ForceMode.VelocityChange);
			
			touchGround = false;
			
		}
		
		
		
		var curSpeed = rigidbody.velocity;
		
		curSpeed.y = 0;
		
		
		
		if (touchGround  curSpeed.magnitude < maxSpeed) {
			
			rigidbody.AddRelativeForce (Acceleration, 0, 0);
			
		}
		
		
		
	}
	
	void OnCollisionEnter(){
		
		touchGround = true;
		
		
		
	}
	
}

Or do i need to change something in the rigidbody?
Mass: 1
Drag: 0,1
Angular Drag: 1
Use Gravity: yes
Is Kinematic: no
Interpolate: None
Collision Detection:: Discrete
Freeze Rotation X Z

2

maybe…