GameObject starts drifting on X axis when doing high jump

Hey guys,my player game object keeps drifting on the X axis when he does a jump off platforms. This especially happens when he is high up, and during the jump I cant control where he lands! Below is my code. I appreciate any help, this issue has been giving me a headache for hours!

 using UnityEngine;
 using System.Collections;

 public class Player : MonoBehaviour {

 // Use this for initialization
 Transform myTransform;
 private float border = 6.5f;

 private float speed = 5f;
 void Start () {
     myTransform = transform;
     this.rigidbody.freezeRotation = true;
 }
 
 // Update is called once per frame
 void Update () {
     myTransform.position = new Vector3(myTransform.position.x, myTransform.position.y, 0f);
     myTransform.rotation = Quaternion.identity;
     if (Input.GetKey(KeyCode.D))
     {
         myTransform.Translate(Vector3.right * Time.deltaTime * speed);
     }
     else if (Input.GetKey(KeyCode.A))
     {
         myTransform.Translate(Vector3.left * Time.deltaTime * speed);
     }

     if (myTransform.position.x > border)
     {

         myTransform.position = new Vector3(-border, myTransform.position.y, myTransform.position.z);
     }
     else if (myTransform.position.x < -border)
     {
         myTransform.position = new Vector3(border, myTransform.position.y, myTransform.position.z);
     }
 }

 void OnCollisionStay2D(Collision2D collision)
 {
     if (collision.gameObject.CompareTag("Platform"))
     {


         if (Input.GetKeyDown(KeyCode.Space))
         {
             //myTransform.Translate(new Vector3(0, 4, 0));
             this.gameObject.rigidbody2D.AddForce(new Vector3(0, 6, 0), ForceMode2D.Impulse);
         }
     }
     
 }
 }