Ball moving much faster forward when there is horizontal input

For some reason, my ball moves a lot faster and increases speed much faster after horizontal input, If you dont move sideways at all, it moves at the rate it should. Here is my snippet of code(in the start function, forwardSpeed = 6)(The code below is in FixedUpdate):

             forwardSpeed += Time.deltaTime * 0.02f;
             #if !UNITY_ANDROID && !UNITY_IPHONE && !UNITY_BLACKBERRY && !UNITY_WINRT || UNITY_EDITOR
             Vector3 editorMovement = new Vector3(Input.GetAxis("Horizontal"), 0.0f, 0.0f);
             rigidbody.AddForce(new Vector3(editorMovement.x * Sidewaysspeed * Time.deltaTime, 0.0f, 0.0f));
             #else
             Vector3 movement = new Vector3 (Input.acceleration.x, 0.0f, 0.0f);
             rigidbody.AddForce (new Vector3(movement.x * Sidewaysspeed * Time.deltaTime, 0.0f, 0.0f));
             #endif
             rigidbody.AddForce (new Vector3 (0.0f, 0.0f, forwardSpeed));