Game not working correctly in build mode?

i created a 2D game in unity 5 with a menu as a separate scene that takes you to the game on button press, but once build the game screen still shows a bit of the menu on the right of the screen. the camera for the menu and the game are the exact same size and they work fine in unity, i tried a few different settings like free aspect and 16:9 but it always happens. i have no idea why it occurs and is the last obstacle to overcome before i can hand this in. below is an example of the problem and the code i used to transition between scenes.

The Problem: (http://i.imgur.com/L7mXcr3.png)

Script for transition wrote in C# (most of this code is for button positioning on the menu): using UnityEngine; using System.Collections;

 public class MainMenu : MonoBehaviour {
 
     public Texture backgroundTexture;
     public GUIStyle Random1;
     public GUIStyle Random2;
     public float guiPlacementY;
     public float guiPlacementX;
     public float guiPlacementY2;
     public float guiPlacementX2;
     void OnGUI(){
         GUI.DrawTexture (new Rect (0, 0, Screen.width, Screen.height), backgroundTexture);
 
         //PLAY
         if (GUI.Button (new Rect(Screen.width * guiPlacementX, Screen.height * guiPlacementY, Screen.width * .5f, Screen.height * .2f),"", Random1)){
             Application.LoadLevel ("ArrowDash");
         }
         //QUIT
         if (GUI.Button (new Rect(Screen.width * guiPlacementX2, Screen.height * guiPlacementY2, Screen.width * .45f, Screen.height * .2f),"", Random2)){
         Application.Quit();
         }
     }
 }