Rotation causing problem in Transform.forward

I have this script,

 void Update () {
 
         float pitch, yaw, roll;
 
         pitch = Input.GetAxis ("Mouse Y");
         yaw = Input.GetAxis ("Mouse X");
         roll=Input.GetAxis ("Roll");
 
 
         transform.Rotate (-pitch, yaw, -roll);
 
 
 
 
         if (Input.GetKey (KeyCode.W))
             Rigid.AddRelativeForce (transform.forward * 50);
         else if (Input.GetKey (KeyCode.S))
             Rigid.AddRelativeForce (-transform.forward * 50);
         else if (Input.GetKey (KeyCode.D))
             Rigid.AddRelativeForce (transform.right * 50);
         else if (Input.GetKey (KeyCode.A))
             Rigid.AddRelativeForce (-transform.right * 50);
         else
             Rigid.velocity = Vector3.zero;
 
         if (Input.GetKey (KeyCode.Space)) {
             
             
             transform.rotation = Quaternion.Euler (Vector3.zero);
             Rigid.velocity=Vector3.zero;
             Rigid.angularVelocity=Vector3.zero;
         }
         
     }

My "Roll" is defined as 'q' and 'e' keys. "Rigid" is rigidbody object.

I simply want to implement 6DoF on this cube, the pitch, yaw and roll works fine , but when it comes to movement it behaves in very unusual way after the object is rotated, I tried moving by using localPosition still no result. I also used relative torque for rotation but it resulted in worse, that is why rotation is controlled by transform.rotation not torque.

I suppose I am not handling gimbal lock or something? Or am I doing it completely wrong?