Acne dark spot treatments?

For the past 4 years I have suffered from pretty severe cystic acne and subsequent dark spots on my upper arms, which over the past year has spread to my chest, lower arms, and stomach. I have been to my dermatologist who has prescribed 2 washes and 3 different creams, all of which have proved slow to work even after months of usage. I'm wondering if anyone has any recommendations for products they used to clear their body acne. I am open to any suggestions.