Checking for a gameobject at a position

I am trying to make a spawner button for my 2D-TBS game, i have gotten the object to spawn, but i am still trying to make a check to see if there is a game object at that location, other wise i get objects overlapping and pushing each other out of the way, i am drawing a complete blank on how to do it code wise, but i do know i need colliders, so i have place Boxcollider2Ds on everything thats gonna collide with something on the same layer

my code is included below, my objective here is to check if there is a gameobject at a current position, and if there is an object at that position, to spawn the object at a different position instead,

using UnityEngine; using System.Collections; using UnityEngine.UI; using Random = UnityEngine.Random;

public class Mspawn : MonoBehaviour { public Button button; public BoardManager boardManger; public int x; public int y; public Vector3 CheckPosition; void OnEnable(){ if (Input.GetMouseButtonDown(0)) { button.onClick.AddListener (SpawnUnit); }

 }
 void awake(){
     boardManger = GetComponent<BoardManager> ();
 }
 void SpawnUnit()
 {
     /*Debug.Log ("Testing...");
     for (int i = 0; i < boardManger.PlayerUnits.Length; i++) 
     {
     //this code is dysfunctional, im still working on it. just ignore it
         Debug.Log (boardManger.PlayerUnits.Length);
         if (boardManger.PlayerUnits[i] == GameObject.FindWithTag("PlayerSoldierMarksman"))
         {
             Debug.Log("Testing complete");
             Instantiate (boardManger.PlayerUnits[i], new Vector3 (1, 1,0f), Quaternion.identity);
         }
     }*/
     Instantiate (boardManger.PlayerUnits[3], new Vector3 (randomSpawnPosition), Quaternion.identity);
 }
 public void checkPosition(Vector3 check)
 {
     check = randomSpawnPosition ();
          //this is obviously the location for what i'm trying to do;
 }
 Vector3 randomSpawnPosition()
 {
     int x = Random.Range(0,2);
     int y = Random.Range(0,2);
     Vector3 Position = new Vector3 (x, y);
     return Position;

 }

}