Place whole chicken in large stockpot and cover with water. Pour in chicken stock. Add 2 carrots, 2 celery stalks and thyme, a little salt and pepper, and bring to a boil. Cook at a hard simmer for about an hour, until chicken is done and tender. Remove chicken from pot and discard the carrots, celery, and thyme stalks.While chicken is cooling, add all of the vegetables to the pot along with salt and pepper.Shred chicken and add to the pot.Bring to a boil, then turn down to hard simmer for an hour, stirring frequently.Season to taste.