Lentil Soup with oregano

1 (12 ounce) bag lentils , sorted and rinsed 2 lbs diced ham 4 stalks celery , thinly sliced 4 carrots , diced 1 medium onion , diced 8 -10 button mushrooms ,[...]

3 cups vegetable broth 3 cups water 2 cups brown lentils , picked over and rinsed 1 tablespoon olive oil 1 large onion , peeled and coarsely chopped 2 large[...]