How to have a GUI button be made at the position of it's attached transform?

I am trying to make it so I can make a button wherever I drag the game object to. This is my latest working code:

 using UnityEngine;
 using System.Collections;
 
 public class ButtonScript : MonoBehaviour {
     public Texture2D icon;
     public float posX; 
     public float posY; 
     public string LevelToLoad;
     public int sizeX;
     public int sizeY;
     Vector3 thisposition;
 
     // Use this for initialization
     void Start () {
         posX = this.transform.position.x;
         posY = this.transform.position.y;
         thisposition = Camera.main.WorldToScreenPoint (new Vector3 (posX, posY, 0));
 
     }
 
     void OnGUI()
     {
         GUI.backgroundColor = Color.red;
         if (GUI.Button (new Rect (thisposition.x, thisposition.y, sizeX, sizeY), icon)) {
                         Application.LoadLevel (LevelToLoad);
                 }
     }
     
     // Update is called once per frame
     void Update () {
 
     }
 
 }

the only problem is the Y axis is inverted and I can't figure out how to fix the Y co-ord so it's not inverted. Thanks for any help!