Thank you for your enquiry. I’m so sorry to hear that you’re having this problem. Unfortunately, having the type of skin that you have, means that you are prone to pigment very easily, so your skin will get darker very, very easily. There are a few things you need to be VERY disciplined about. You need to make sure you use a lip product that has a high SPF everyday.
I would also suggest you use a serum that can help you lighten and prevent further pigmentation from forming every day. Something like “Brighter Concentrate” from Lamelle or Lymixyl. You can still wear your make up and lipstick over these products.