How to add multitouch?

I can't move sideways and jump at the same time. I've tried some techniques, but my scripting skills are still very low. If possible just say where should the needed code go and explain a little bit. Here is my code:

 using UnityEngine;
 using System.Collections;
 [RequireComponent(typeof (Rigidbody2D))]
 [RequireComponent(typeof(CircleCollider2D))]
 public class TouchControlsV2 : MonoBehaviour 
 {    
     // GUI textures
     public GUITexture guiLeft;
     public GUITexture guiRight;
     public GUITexture guiJump;    
     // Movement variables
     public float moveSpeed = 5f;
     public float oppMoveSpeed = -5f;
     public float jumpForce = 50f;
     public float maxJumpVelocity = 2f;    
     //public float tapCount = 2;
     // Movement flags
     private bool moveLeft, moveRight, doJump = false;
     void Update () 
     {
         if (Input.touchCount > 0)
         {
             Touch t = Input.GetTouch(0);
             if (t.phase == TouchPhase.Began)
             {
                 if (guiLeft.HitTest(t.position, Camera.main))
                 {
                     moveLeft = true;
                 }                
                 if (guiRight.HitTest(t.position, Camera.main))
                 {
                     moveRight = true;
                 }                
                 if (guiJump.HitTest(t.position, Camera.main))
                 {
                     doJump = true;
                 }
             }            
             if (t.phase == TouchPhase.Ended)
             {
                 doJump = moveLeft = moveRight = false;
             }
         }        
     }    
     void FixedUpdate()
     {
         if (moveLeft)
         {
             rigidbody2D.velocity = new Vector2 (oppMoveSpeed, rigidbody2D.velocity.y);
         }        
         if (moveRight)
         {
             rigidbody2D.velocity = new Vector2 (moveSpeed, rigidbody2D.velocity.y);
         }    
         if (doJump)
         {
             if (rigidbody2D.velocity.y < maxJumpVelocity)
             {
                 rigidbody2D.AddForce(Vector2.up * jumpForce);
             } 
             else
             {
                 doJump = false;
             }
         }
     }
 }