Level Selection menu, camera boundary unity 2d - unity3d

Question

My level selection menu scene will be a graphic map. Think level selection similar to candy crush. I have different sprites for different maps that will be instantiated when the user moves the camera to that map. In order for me to achieve this, I scroll/move the camera using touch on it's Y-axis. But the problem is, I'm having a trouble getting the boundary of the map sprite, I already read a lot of solution about this one. Here is my current script. I don't know what I'm doing wrong. My camera got stuck when it is near the boundary. Thank you for your help
public float scrollSpeed = 10.0f;
public GameObject[] maps;
Camera mainCamera;
private float topBound;
private float bottomBound;
private Vector3 pos;
private SpriteRenderer currentSprite;
private int mapIndex;
void Awake ()
{
mapIndex = 0;
mainCamera = Camera.main;
currentSprite = maps [mapIndex].GetComponent<SpriteRenderer> ();
bottomBound = currentSprite.sprite.bounds.size.y * -1;
topBound = currentSprite.sprite.bounds.size.y + currentSprite.gameObject.transform.position.y;
}
void Update ()
{
if (Input.touchCount > 0 && Input.GetTouch (0).phase == TouchPhase.Moved)
{
Vector2 touchDeltaPosition = Input.GetTouch(0).deltaPosition;
mainCamera.transform.Translate(0f,-touchDeltaPosition.y * scrollSpeed * Time.deltaTime,0f);
}
}
private float getAxisDelta(float axisDelta,float camMin,float camMax,float bottom,float top)
{
//get where edge of camera will have moved if full translate is done
float boundaryMinPixelsDestination = camMin - Mathf.Abs(axisDelta);
float boundaryMaxPixelsDestination = camMax + Mathf.Abs(axisDelta);
Debug.Log("MaxPixels:"+boundaryMaxPixelsDestination+"="+camMax+"+"+Mathf.Abs(axisDelta));
//check to see if you're within the border
if ((boundaryMinPixelsDestination <= bottom && axisDelta > 0) ||
(boundaryMaxPixelsDestination >= top && axisDelta < 0))
{
axisDelta = 0;
}
return axisDelta;
}
private float camBoundPos(string pos)
{
float bounds = 0f;
if (pos == "top")
bounds = mainCamera.transform.position.y + mainCamera.orthographicSize;
if(pos == "bottom")
bounds = mainCamera.transform.position.y - mainCamera.orthographicSize;
return bounds;
}