How to keep Y velocity normal?

I’ve got a 2D object with a rigidbody2D attached but it falls really slowly for some reason. I’m using velocity to move it left or right but I want the falling movement on the Y axis to be normal. How would I do this?

  private Vector2 velocity;

    [SerializeField]
    public Rigidbody2D rb;
    public float mouseSpeed;

    void Update()
    {
        if (Input.GetMouseButtonUp(0))
        {
            velocity = new Vector2(mouseSpeed, 0);
        }
    }
    void FixedUpdate()
    {
        rb.velocity = velocity;
    }

you are setting the velocity to 0, just dont change it

velocity = new Vector2(mouseSpeed, rb.velocity.y);