Rigidybody2D addforce at constant speed

Attempting an infinite 2d runner, but when I use rigibody2D.addforce it slowly accelerates to insanely fast regardless of what I multiply it by…

enter code here#pragma strict

var myForce : float = 20;
var jumpForce : float = 600;


function Update()
        {
          if(Input.GetKeyDown(KeyCode.Space))
        	{
            rigidbody2D.AddForce(new Vector2(0, jumpForce ));
        	}
        }


function FixedUpdate () {

		rigidbody2D.AddForce(new Vector2(myForce, 0));

};

Even if I change myForce to 10 it starts slowly and eventually picks up crazy amounts of speed. All I want is a constant movement speed. Thanks in advance.

I believe rigidbody.Addforce() adds the force to the current velocity, meaning you actually speed up your game object by “myForce” every time fixed update is called. Try calling it only once