Health bar goes down immediately

I had numeric health and now i want to change it to a sliding health bar using an image because a lot of people are complaining that numeric health is to distracting. I am trying to test a healthbar while still having the numeric code (for now). Instead of the healthcare going down slowly as the character gets hit it goes to 0 immediately. Please help.

 using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 
 public class PlayerHealth : MonoBehaviour {
 
     public Text Health;
 
     public GameMan gameMan;
     public int maxHp = 100;
     public int currentHp;
     public Image currentHealthbar;
 //    public GameObject HealthPickup;
 
     // Use this for initialization
     void Start () {
         currentHp = maxHp;
         Health.text = "Health: " + maxHp;
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 
     void OnCollisionEnter(Collision col)
     {
 
         Follow foll = col.gameObject.GetComponent<Follow> ();
         if (foll != null)
         {
             Damage(foll.damage);
         }
     }
     void OnTriggerEnter(Collider gameObject)
     {
         if (gameObject.tag == "health")
         {
             currentHp = currentHp + 1000;
         }
     }
 
 
     void Damage(int damageToTake)
     {
         float ratio = 1 / maxHp;
         currentHp -= damageToTake;
         Health.text = "Health: " + currentHp;
         currentHealthbar.rectTransform.localScale = new Vector3 (ratio, 1, 1);
         if (currentHp <= 0) {
             Die ();
         }
     }
 
     void Die()
     {
         gameMan.Death (); 
     }
 //    void OnColliderEnter(Collider HealthPickup){
 //        Debug.Log ("health boosted");
 //            currentHp= 100;
 //    }
 }