Simple Object Dragging

Hello all. I'm at a game jam right now, time's running low, and I'm stuck with this object dragging.

//////

 using UnityEngine;
 using System.Collections;
 
 public class Dragable : MonoBehaviour {
     
     bool dragging;
     RaycastHit hit;
 
     // Use this for initialization
     void Start () {
         dragging = false;
     }
     
     // Update is called once per frame
     void Update () {
         if(Input.GetMouseButtonDown(0) && collider.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition),out hit, Mathf.Infinity)){
             Debug.Log ("Clicked Biyatch!");
             dragging = true;
         }
         if (dragging == true){
             Vector3 mpos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
             float tx = mpos.x;
             float ty = mpos.y;
             rigidbody.MovePosition(new Vector3(tx,ty,transform.position.z));
         }
     }
     
     void onMouseDown() {
         Debug.Log("Click");
         if (dragging == false){
             dragging = true;
         }
     }
         
     void onMouseUp(){
         if (dragging == true) {
             dragging = false;
         }
     }
 }

This registers a click, and it's supposed to update the object position to the mouse x/y. It's crude but I'm trying to do it quickly so I can move on.

What winds up happening is when I click, it sets the transform to the center of the camera. Can't find why it's doing that. Am I using anything incorrectly?