how do i fix how i make triangels in my mesh

 [RequireComponent(typeof(MeshFilter))]
 public class MeshGenerator : MonoBehaviour
 {
     Mesh mesh;
 
     //int[] triangles;
     //Vector3[] vertices;
     List<Vector3> vertices;
     List<int> triangles;
 
     public int y;
     public int x;
     public int z;
 
     int totalVertices;
 
     int currentY;
     int currentX;
     int currentZ;
 
     int point;
 
     public bool updateMesh;
 
     void Start ()
     {
         mesh = new Mesh();
         GetComponent<MeshFilter>().mesh = mesh;
 
         totalVertices = y * x;
 
         CreateShape();
         UpdateMesh();
     }
 
     void CreateShape()
     {
         vertices = new List<Vector3>(totalVertices);
         for (int i = 0; i < totalVertices; i++)
         {
             //currentZ = Random.Range(0, 10);
             vertices.Add(new Vector3(currentX, currentZ, currentY));
             if(currentX < x - 1)
             {
                 currentX++;
             }else 
             if(currentY < y - 1)
             {
                 currentY++;
                 currentX = 0;
             }
         }
 
         triangles = new List<int>(0);
         for (int i = 0; i < totalVertices - x; i++)
         {
             triangles.Add(i);
             triangles.Add(i + x);
             triangles.Add(i + 1);
         }
 
         for (int i = 0; i < totalVertices - x; i++)
         {
             triangles.Add(i);
             triangles.Add(i + x - 1);
             triangles.Add(i + x);
         }
 
     }
     
     void UpdateMesh()
     {
         mesh.Clear();
 
         Vector3[] verticesArray;
         verticesArray = vertices.ToArray();
 
         int[] trianglesArray;
         trianglesArray = triangles.ToArray();
 
         mesh.vertices = verticesArray;
         mesh.triangles = trianglesArray;
 
         mesh.RecalculateNormals();
     }
 }

there is something wrong with how i make the triangles but i dont know how to fix it