Need help with dash ability

So I'm trying to make a 2D fighter and basically what I'm trying to do is give my character a simple dash ability where while running they can press the a attack button to dash forward a bit. The problem is that after a few dashes my stamina variable will go up infinity and i don't know why. Here is the character code I'm using. Its a mess but any help would be much appreciated:

using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI;

public class BlueControls : MonoBehaviour {

 [HideInInspector] public bool facingLeft = true;

 public Text dashCheck;
 public bool dashing = false;
 public float dashMultiplier = 8;
 public bool canDash = true;
 public float dashTime = 0.5f;
 public float dashRegen = 2f;
 private int stamina = 2;
 public bool jump = false;
 public float moveForce = 365f;
 public float maxSpeed = 5f;
 public float jumpForce = 1000f;
 public Transform GroundCheck;

 private bool grounded = true;
 private Animator anim;
 private Rigidbody2D rb2d;

 void Awake () {
     anim = GetComponent<Animator> ();
     rb2d = GetComponent<Rigidbody2D> ();

 }


 void Update () {
     dashCheck.text = ("Stamina = " + stamina);
     grounded = Physics2D.Linecast (transform.position, GroundCheck.position, 1 << LayerMask.NameToLayer ("Ground"));
     if (Input.GetButtonDown ("Blue Jump") && grounded) {
         jump = true;
     }
     if (Input.GetButtonDown ("Blue Fire1") && !Input.GetButton("Blue Horizontal")){
         anim.SetTrigger ("Basic Attack");
     }
     if (Input.GetButtonDown ("Blue Fire2") && !Input.GetButton("Blue Horizontal")) {
         anim.SetTrigger ("Heavy Attack");
     }
     if (Input.GetButton ("Blue Fire3") && !Input.GetButton("Blue Horizontal")) {
         anim.SetBool ("Block", true);
     } else {
         anim.SetBool ("Block", false);
     }
 }
 void FixedUpdate(){
     float h = Input.GetAxis ("Blue Horizontal");
     anim.SetFloat("Speed", Mathf.Abs(h));
     if (h * rb2d.velocity.x < maxSpeed && !Input.GetButton ("Blue Fire2") && !Input.GetButton ("Blue Fire3")) {
         rb2d.AddForce (Vector2.right * h * moveForce);
     }
     if (Input.GetButtonDown("Blue Fire1") && !Input.GetButton("Blue Fire2") && !Input.GetButton("Blue Fire3") && stamina > 0 && canDash){
         rb2d.AddForce (Vector2.right * h * moveForce *dashMultiplier);
         dashing = true; 
         StartCoroutine("dtdt");
         anim.SetTrigger ("Dash Attack");
     }
     if (stamina == 0) {
         StopCoroutine ("dtdt");
         StartCoroutine ("dtdf");
         dashing = false;
         canDash = false;
     }
     if (stamina == 2) {
         StopCoroutine ("dtdf");
         canDash = true;
     }
     if (Mathf.Abs (rb2d.velocity.x) > maxSpeed && dashing == false ){
         rb2d.velocity = new Vector2 (Mathf.Sign (rb2d.velocity.x) * maxSpeed, rb2d.velocity.y);
     }
     if (h < 0 && !facingLeft){
         Flip ();
     }
     else if (h > 0 && facingLeft){
         Flip ();
     }
     if (jump) {
         anim.SetTrigger ("Jump");
         rb2d.AddForce (new Vector2 (0f, jumpForce));
         jump = false;
     }
     if (grounded) {
         anim.SetBool ("landed", true);
         } else {
         anim.SetBool ("landed", false);
     }
 }


 void Flip (){
     facingLeft = !facingLeft;
     Vector3 theScale = transform.localScale;
     theScale.x *= -1;
     transform.localScale = theScale;
 }
 IEnumerator dtdt(){
     while (true) {
         yield return new WaitForSeconds (dashTime);
         stamina -=2;
     }
 }
 IEnumerator dtdf(){
     while (true) {
         yield return new WaitForSeconds (dashRegen);
         stamina += 1;
     }
 }

}