How to treat post-inflammatory hyper-pigmentation scars on face, neck and breasts? (photos)

I'm a biracial women with brown PIH scars on my face, neck and breasts (around the nipples) from acne, ingrown hairs and compulsive skin picking. I've been using Tretinoin (0.05% strength), as prescribed by my dermatologists for three months. My acne has improved, but the PIH scars remain the same. I want a second opinion. I need a more effective treatment for the PIH/discolorations, that has minimal risks and yields faster results. What are my options?