Enemy Spawn Script Spawning Infinite Enemies [Help]

I'm trying to test my enemy spawn script (c#), and I thought I had it pretty well figured out. For the meantime it's all attached to my enemy prefab, but eventually I will attach it to the player. This is how the script is supposed to work:

1. In the start function, check how many objects have the tag "Enemy".

2. If it's greater than 0 (for testing) run the StartLevel function, passing a levelIndex variable.

3. In StartLevel, do some things (not implemented), then call SpawnEnemy, passing the number of enemies to spawn.

4. In SpawnEnemy, for each enemy that needs to be spawned, find a random point around the player (x,z), then pass that point to a function that finds the terrain height at this point. If it returns a valid number, and passes some other conditions (isn't too close to player, or too close to other spawned enemies) spawn this enemy, facing the player.

5. Save this spawn point as the lastSpawnPoint for any other enemies that need spawning.

Here is the relevant code:

  using UnityEngine;
     using System.Collections;
     
     public class EnemyScript : MonoBehaviour {
     
         public Transform playerPos;
         public float enemySpeed = 5f;
         public float detectionRadius = 150;
         public CharacterController cc;
         public GameObject enemyPrefab;
         public bool sawPlayer = false;
         public Vector3 playerDirection = Vector3.zero;
         public float verticalSpeed;
         public float spawnDistance = 50.0f;
         public float minEnemySpawnDensity = 6f;
         public float minSpawnDistance = 20f;
         public int spawnThisMany = 0;
     
     
         // Use this for initialization
         void Start () {
 
                 //get the transform of the player
             playerPos = GameObject.FindWithTag("Player").transform;
 
                 //get the character controller attached to the enemyPrefab
             cc.GetComponent<CharacterController>();
 
                 //if there are no enemies present, start level 1
             if(GameObject.FindGameObjectsWithTag("Enemy").Length >= 0){
                 StartLevel(spawnThisMany);
             }
     
         }
     
         //this function handles the spawning of enemies around you. It is called
         //from the startLevel function, which handles the number of enemies in 
         //each level.
         void SpawnEnemy(int numberOfEnemies){
 
                 //find a random point around the player
             Vector3 spawnPoint = Random.insideUnitCircle.normalized*spawnDistance;
             Vector3 lastSpawnPoint = Vector3.zero;
 
                 //this sets the spawn point height to the terrain height, plus a the radius of the sphere's character controller
             spawnPoint.y = TerrainHeight(spawnPoint) + cc.radius;
 
                 for(int enemyCount = 0; enemyCount < numberOfEnemies; enemyCount++){
 
                         //if terrain height returns infinity, or the difference in this spawn
                 //point and the last spawn point is greater than the minimus spawn
                 //density, or the enemy spawns to close to the player, start over.
                 if(spawnPoint.y == Mathf.Infinity || (spawnPoint - lastSpawnPoint).magnitude <= minEnemySpawnDensity || (spawnPoint - playerPos.position).magnitude <= minSpawnDistance){
                     SpawnEnemy(numberOfEnemies - enemyCount);
                 }
 
                         //if all the conditions are met, an enemy is spawned facing the player,
                 //and the spawn point is saved as the last spawn point.
                 else{
                     //setting look direction for enemy, cancelling out the y portion
                     Vector3 lookDirection = playerPos.position;
                     lookDirection.y = 0f;
                     Instantiate(enemyPrefab,spawnPoint,Quaternion.LookRotation(lookDirection));
                     lastSpawnPoint = spawnPoint;
                 }
             }
     
         }
 
         //this starts each level
         void StartLevel(int levelIndex){
                 //do stuff here
             SpawnEnemy (levelIndex);
         }
 
         //TerrainHeight finds the height of the terrain given a 2D position vector
         float TerrainHeight(Vector2 spawnPoint){
 
             //declare a raycast hitpoint
             RaycastHit hitPoint;
 
             //go to spawnPoint and cast a ray upwards, if it hits return that y position.
             //if it doesn't, shoot a ray downwards and it should hit, if not, return infinity.
             if(Physics.Raycast(spawnPoint,Vector3.up, out hitPoint)){
                 return hitPoint.transform.position.y;
             }
             else if(Physics.Raycast(spawnPoint,Vector3.down, out hitPoint)){
                 return hitPoint.transform.position.y;
             }
             else{
                 return Mathf.Infinity;
             }
         }
     }
     

I'm pretty sure the problem lies within my for statement, although for the life of me I can't figure it out. It's probably something silly. But everytime I go to play mode, the enemies just keep piling up and lagging my game. About 150 spawn before I can get out of play mode. Thanks for any help.