GUI Button Moving with a mouse

Heya! I've got another question. here is my code (written with a lot of help here in forum!) :

using UnityEngine; using UnityEngine.UI; using System.Collections;

public class ClickOnAlarm : MonoBehaviour { private bool showText = false;

 void OnMouseDown()
 {
     if (!showText)
         showText = true;
 
 }

 void OnGUI()
 {

     if (showText)
     {
         var x = Event.current.mousePosition.x;
         var y = Event.current.mousePosition.y;

         if(GUI.Button (new Rect (x -150, y +50, 300, 60), "Anlage braucht dringend Wartung")) // Position und Größe des Buttons

             showText = false;
     }
 }

}

now what my problem is, is that the GUI Button moves with my mouse. what i want is that my button appears when i click on an object (herefor mouseposition), and STAYS there, when i move my mouse away, before i close the button with another mouseclick.

pleeeease help me! :>