Draw Line and detect line collision

I have this code. Its work fine. The line are drawing and detect collision but its too sesitive. When i made a sharp corner or accidentally i little bit draw backwards immediately detect the collision. How can i do that the last 1 unit do not detect.

heres more abot the script: http://www.theappguruz.com/blog/draw-line-mouse-move-detect-line-collision-unity2d-unity3d

using UnityEngine; using System.Collections; using System.Collections.Generic; public class DrawLine : MonoBehaviour { private LineRenderer line; private bool isMousePressed; public List pointsList; private Vector3 mousePos;

 // Structure for line points
 struct myLine
 {
     public Vector3 StartPoint;
     public Vector3 EndPoint;
 };
 //    -----------------------------------    
 void Awake ()
 {
     // Create line renderer component and set its property
     line = gameObject.AddComponent<LineRenderer> ();
     line.material = new Material (Shader.Find ("Particles/Additive"));
     line.SetVertexCount (0);
     line.SetWidth (0.1f, 0.1f);
     line.SetColors (Color.green, Color.green);
     line.useWorldSpace = true;    
     isMousePressed = false;
     pointsList = new List<Vector3> ();
     //        renderer.material.SetTextureOffset(
 }
 //    -----------------------------------    
 void Update ()
 {
     // If mouse button down, remove old line and set its color to green
     if (Input.GetMouseButtonDown (0)) {
         isMousePressed = true;
         line.SetVertexCount (0);
         pointsList.RemoveRange (0, pointsList.Count);
         line.SetColors (Color.green, Color.green);
     }
     if (Input.GetMouseButtonUp (0)) {
         isMousePressed = false;
     }
     // Drawing line when mouse is moving(presses)
     if (isMousePressed) {
         mousePos = Camera.main.ScreenToWorldPoint (Input.mousePosition);
         mousePos.z = 0;
         if (!pointsList.Contains (mousePos)) {
             pointsList.Add (mousePos);
             line.SetVertexCount (pointsList.Count);
             line.SetPosition (pointsList.Count - 1, (Vector3)pointsList [pointsList.Count - 1]);
             if (isLineCollide ()) {
                 isMousePressed = false;
                 line.SetColors (Color.red, Color.red);
             }
         }
     }
 }
 //    -----------------------------------    
 //  Following method checks is currentLine(line drawn by last two points) collided with line 
 //    -----------------------------------    
 private bool isLineCollide ()
 {
     if (pointsList.Count < 2)
         return false;
     int TotalLines = pointsList.Count - 1;
     myLine[] lines = new myLine[TotalLines];
     if (TotalLines > 1) {
         for (int i=0; i<TotalLines; i++) {
             lines [i].StartPoint = (Vector3)pointsList [i];
             lines [i].EndPoint = (Vector3)pointsList [i + 1];
         }
     }
     for (int i=0; i<TotalLines-1; i++) {
         myLine currentLine;
         currentLine.StartPoint = (Vector3)pointsList [pointsList.Count - 2];
         currentLine.EndPoint = (Vector3)pointsList [pointsList.Count - 1];
         if (isLinesIntersect (lines [i], currentLine)) 
             return true;
     }
     return false;
 }
 //    -----------------------------------    
 //    Following method checks whether given two points are same or not
 //    -----------------------------------    
 private bool checkPoints (Vector3 pointA, Vector3 pointB)
 {
     return (pointA.x == pointB.x && pointA.y == pointB.y);
 }
 //    -----------------------------------    
 //    Following method checks whether given two line intersect or not
 //    -----------------------------------    
 private bool isLinesIntersect (myLine L1, myLine L2)
 {
     if (checkPoints (L1.StartPoint, L2.StartPoint) ||
         checkPoints (L1.StartPoint, L2.EndPoint) ||
         checkPoints (L1.EndPoint, L2.StartPoint) ||
         checkPoints (L1.EndPoint, L2.EndPoint))
         return false;
     
     return((Mathf.Max (L1.StartPoint.x, L1.EndPoint.x) >= Mathf.Min (L2.StartPoint.x, L2.EndPoint.x)) &&
         (Mathf.Max (L2.StartPoint.x, L2.EndPoint.x) >= Mathf.Min (L1.StartPoint.x, L1.EndPoint.x)) &&
         (Mathf.Max (L1.StartPoint.y, L1.EndPoint.y) >= Mathf.Min (L2.StartPoint.y, L2.EndPoint.y)) &&
         (Mathf.Max (L2.StartPoint.y, L2.EndPoint.y) >= Mathf.Min (L1.StartPoint.y, L1.EndPoint.y)) 
            );
 }

}