[C#, 2D] How do I apply force to a player using vector 3 velocity to move

Forgive me if I can't describe the issue well enough, but I'm trying to use AddForce to 'boost' my player forward, but to use addForce i have to suspend my rigidbody's normal movement code, since they boh use X velocity. The issue is that when my player is done 'dashing' they will stop mid air, and not carry the velocity forward.

My regular movement code is

  void FixedUpdate()
     {
         if (isDashing == false)
         {
         if (isSliding == false)
         {
             if (touchWall == false)
             {
                 playerBody.gravityScale = 1.5f; 
                 Vector3 moveVelocity = new Vector3(Input.GetAxis("moveX") * (playerSpeed * 50.0f) * Time.fixedDeltaTime, playerBody.velocity.y, 0.0f);
                 playerBody.velocity =  moveVelocity;
                 
             }
                 if (touchWall == true)
                 {
                     playerBody.gravityScale = 0f;
                     Vector3 moveVelocity = new Vector3(Input.GetAxis("moveX") * (playerSpeed * 50.0f) * Time.fixedDeltaTime, Input.GetAxis("moveY") * (playerSpeed * 50.0f) * Time.fixedDeltaTime, 0.0f);
                     playerBody.velocity = moveVelocity;
 
                 }
             }
         }
         
     }

My Dashing code is

 void Dash()
     {
         if (right == false)
         {
             turnt = -1;
         } else if (right == true)
         {
             turnt = 1;
         }
         
             Vector3 moveVelocity = new Vector3((slideSpeed * 50.0f * turnt) * Time.fixedDeltaTime, playerBody.velocity.y, 0.0f);
             playerBody.velocity = moveVelocity;
             StartCoroutine("DashW8");
     }
 
     IEnumerator DashW8()
     {
         yield return new WaitForSeconds(slideW8);
         isDashing = false;
     }