Multiple Constant Force Inputs at once?

I have some modified code from a post on here, by a user named OoglyWoogly I believe, and I have added input for the mouse and keyboard, the keyboard as a backup. When moving the mouse along an axis, x or y, it only uses one input at a time, and I believe it's due to how constant force works. Would anyone be able to assist me, so that the object, being a spacecraft, will pitch/yaw at the same time depending on the mouse location?

 private var previousMousePosition : Vector3;
 
 var LThruster : ParticleSystem;   
 var RThruster : ParticleSystem;   
 var pilot : Rigidbody;
 var invertPitch : boolean = true;
 var invertYaw : boolean = false;
 var sensitivity : float = 1.0;
  
 function Start () 
 {
     //LThruster = GetComponentsInChildren.tag("LThruster");
     LThruster.Stop(true);
     //RThruster = transform.Find("RThruster");
     RThruster.Stop(true);
     rigidbody.AddForce(0,0,0);
 }
 function Update () {
     // Did the user press fire?
     //if (Input.GetButton ("Fire1"))
      //   BroadcastMessage("Fire");
  
     if (Input.GetKeyDown("w"))
     {
         SetThrust(600);
         LThruster.Play(true);
         RThruster.Play(true);
  
     }
  
     if (Input.GetKeyUp("w"))
     {
         SetThrust(0);
         LThruster.Stop(true);
         RThruster.Stop(true);
  
     }
  
     if (Input.GetKeyDown("s"))
     {
         SetThrust(-500);
  
     }
  
     if (Input.GetKeyUp("s"))
     {
         SetThrust(0);
         LThruster.Stop(true);
         RThruster.Stop(true);
     }
  
     if (Input.GetKeyDown("q"))
     {
         SetRoll(400);    
  
     }
  
     if (Input.GetKeyUp("q"))
     {
         SetRoll(0);
  
     }
  
     if (Input.GetKeyDown("e"))
     {
         SetRoll(-400);   
  
     }
  
     if (Input.GetKeyUp("e"))
     {
         SetRoll(0);
  
     }
  
         if (Input.GetKeyDown("i"))
     {
         SetPitch(375);
  
     }
  
     if (Input.GetKeyUp("i"))
     {
         SetPitch(0);
  
     }
  
     if (Input.GetKeyDown("k"))
     {
         SetPitch(-375);  
  
     }
  
     if (Input.GetKeyUp("k"))
     {
         SetPitch(0);
  
     }
  
         if (Input.GetKeyDown("j"))
     {
         SetYaw(355);  
  
     }
  
     if (Input.GetKeyUp("j"))
     {
         SetYaw(0);
  
     }
  
     if (Input.GetKeyDown("l"))
     {
         SetYaw(-355); 
  
     }
  
     if (Input.GetKeyUp("l"))
     {
         SetYaw(0);
  
     }
     
     if (Input.GetKeyDown("space"))
     {
         ThrustUp(300);
     }
  
     if (Input.GetKeyUp("space"))
     {
         ThrustUp(0);
     }
     
     if (Input.GetKeyDown(KeyCode.LeftControl))
     {
         ThrustUp(-300);
     }
  
     if (Input.GetKeyUp(KeyCode.LeftControl))
     {
         ThrustUp(0);
     }
     //Testing for mouse
     if (Input.GetAxis("Mouse Y"))
     {
         SetPitch((Input.mousePosition.y - (Screen.height / 2)) * 2);
         Debug.Log((Input.mousePosition.y - (Screen.height / 2)) * 2);//debug
     }
     if (Input.GetAxis("Mouse X"))
     {
         SetYaw((Input.mousePosition.x - (Screen.width / 2)) * 2);
         Debug.Log((Input.mousePosition.x - (Screen.width / 2)) * 2);//debug
     }
 }
  
 function SetThrust ( thrustForce : int)
     {
         pilot.constantForce.relativeForce = Vector3.forward * thrustForce * sensitivity;
     }
 
 function ThrustUp ( thrustForce : int)
     {
         pilot.constantForce.relativeForce = Vector3.up * thrustForce * sensitivity;
     }
  
 function SetRoll (rollForce : int)
     {
         pilot.constantForce.relativeTorque = Vector3(0,0,1) * rollForce * sensitivity;
     }
  
 function SetPitch (pitchForce : int)
     {
         if(invertPitch)
         {
             pilot.constantForce.relativeTorque = Vector3.right * pitchForce * sensitivity;
         }
         else
         {
             pilot.constantForce.relativeTorque = Vector3.left * pitchForce * sensitivity;
         }
     }
  
 function SetYaw (yawForce : int)    
 {
     if(invertYaw)
         {
             pilot.constantForce.relativeTorque = Vector3(0,1,0) * yawForce * sensitivity;
         }
         else
         {
             pilot.constantForce.relativeTorque = Vector3(0,-1,0) * yawForce * sensitivity;
         }
  
 }

Quick Edit: I've noticed that it doesn't happen only the mouse based axis, but instead, any multiple axis edit