panning & zooming using multitouch

This is a script I used a couple of times.. Should fix your problem.. You can remove the HasReachedBounds method. The code might need some modification. Usually works straightforward for me.

 // Just add this script to your camera. It doesn't need any configuration.
 
 using UnityEngine;
 
 public class TouchCamera : MonoBehaviour {
     Vector2?[] oldTouchPositions = {
         null,
         null
     };
     Vector2 oldTouchVector;
     float oldTouchDistance;
 
     private Camera camera;
 
     public SpriteRenderer mapSprite;
 
     Vector3 spriteMin;
     Vector3 spriteMax;
 
     private void Start()
     {
         camera = GetComponent<Camera>();
 
         Bounds spriteBounds = mapSprite.bounds;
         spriteMin = spriteBounds.min;
         spriteMax = spriteBounds.max;
     }
 
     enum BoundReached
     {
         left,
         right,
         top,
         bottom
     }
 
     BoundReached boundReached = BoundReached.left;
 
 
     void Update()
     {
 
         if (HasReachedBounds())
         {
             //lerp back
             if (Input.touchCount == 0)
             {
                 var vertExtent = camera.orthographicSize;
                 var horzExtent = vertExtent * Screen.width / Screen.height;
 
                 if (boundReached == BoundReached.left)
                 {
                     transform.position = Vector3.Lerp(transform.position, new Vector3(spriteMin.x + horzExtent + 1, transform.position.y, transform.position.z), Time.deltaTime * 5);
                 }
                 else if (boundReached == BoundReached.right)
                 {
                     transform.position = Vector3.Lerp(transform.position, new Vector3(spriteMax.x - horzExtent - 1, transform.position.y, transform.position.z), Time.deltaTime * 5);
                 }
                 else if (boundReached == BoundReached.top)
                 {
                     transform.position = Vector3.Lerp(transform.position, new Vector3(transform.position.x, spriteMax.y - vertExtent - 1, transform.position.z), Time.deltaTime * 5);
                 }
                 else if (boundReached == BoundReached.bottom)
                 {
                     transform.position = Vector3.Lerp(transform.position, new Vector3(transform.position.x, spriteMin.y + vertExtent + 1, transform.position.z), Time.deltaTime * 5);
                 }
             }
             
         }
         else
         {
             if (Input.touchCount == 0)
             {
                 oldTouchPositions[0] = null;
                 oldTouchPositions[1] = null;
             }
             else if (Input.touchCount == 1)
             {
                 if (oldTouchPositions[0] == null || oldTouchPositions[1] != null)
                 {
                     oldTouchPositions[0] = Input.GetTouch(0).position;
                     oldTouchPositions[1] = null;
                 }
                 else
                 {
                     Vector2 newTouchPosition = Input.GetTouch(0).position;
 
                     transform.position += transform.TransformDirection((Vector3)((oldTouchPositions[0] - newTouchPosition) * camera.orthographicSize / camera.pixelHeight * 2f));
 
                     oldTouchPositions[0] = newTouchPosition;
                 }
             }
             else
             {
                 if (oldTouchPositions[1] == null)
                 {
                     oldTouchPositions[0] = Input.GetTouch(0).position;
                     oldTouchPositions[1] = Input.GetTouch(1).position;
                     oldTouchVector = (Vector2)(oldTouchPositions[0] - oldTouchPositions[1]);
                     oldTouchDistance = oldTouchVector.magnitude;
                 }
                 else
                 {
                     Vector2 screen = new Vector2(camera.pixelWidth, camera.pixelHeight);
 
                     Vector2[] newTouchPositions = {
                     Input.GetTouch(0).position,
                     Input.GetTouch(1).position
                 };
                     Vector2 newTouchVector = newTouchPositions[0] - newTouchPositions[1];
                     float newTouchDistance = newTouchVector.magnitude;
 
                     transform.position += transform.TransformDirection((Vector3)((oldTouchPositions[0] + oldTouchPositions[1] - screen) * camera.orthographicSize / screen.y));
                     //transform.localRotation *= Quaternion.Euler(new Vector3(0, 0, Mathf.Asin(Mathf.Clamp((oldTouchVector.y * newTouchVector.x - oldTouchVector.x * newTouchVector.y) / oldTouchDistance / newTouchDistance, -1f, 1f)) / 0.0174532924f));
                     camera.orthographicSize *= oldTouchDistance / newTouchDistance;
                     camera.orthographicSize = Mathf.Clamp(camera.orthographicSize, 5, 40);
                     transform.position -= transform.TransformDirection((newTouchPositions[0] + newTouchPositions[1] - screen) * camera.orthographicSize / screen.y);
 
                     oldTouchPositions[0] = newTouchPositions[0];
                     oldTouchPositions[1] = newTouchPositions[1];
                     oldTouchVector = newTouchVector;
                     oldTouchDistance = newTouchDistance;
                 }
             }
 
         }
 
 
         
 
         if (HasReachedBounds())
         {
             Debug.Log("has reached left sprite bounds");
         }
     }
 
     bool HasReachedBounds()
     {
         var vertExtent = camera.orthographicSize;
         var horzExtent = vertExtent * Screen.width / Screen.height;
 
         if (transform.position.x - horzExtent < spriteMin.x)
         {
             boundReached = BoundReached.left;
             return true;
         }
         else if (transform.position.x + horzExtent > spriteMax.x)
         {
             boundReached = BoundReached.right;
             return true;
         }
         else if (transform.position.y - vertExtent < spriteMin.y)
         {
             boundReached = BoundReached.bottom;
             return true;
         }
         else if (transform.position.y + vertExtent > spriteMax.y)
         {
             boundReached = BoundReached.top;
             return true;
         }
         else
         {
             return false;
         }
 
 
     }
 }