Creamy Sausage Tortellini Soup

Ground Italian sausage (1 pound)

Onion (diced, 1/2)

Celery (diced, 2 stalks)

Carrots (diced, 2 large)

Garlic (minced, 2 tbsp)

Salt (1/2 tsp)

Pepper (1/8 tsp)

Italian seasoning (1 tbsp)

Chicken broth (low sodium, 4 cups)

Flour (1/4 cup)

Half and half (1 1/2 cup)

Frozen cheese tortellini (19 oz)

Fresh spinach (5 cups)

Milk (1 cup)