What you are dealing with is a bit of hormonal pigmentation, which can be quite stubborn and it is located fairly deep in the skin. So the solution is to ensure you are using products and/or treatments that can reach the affected are of the skin. There are quite a number of options for you. Depending on your budget for your skin, you could try anything from the Dermamelan treatment mask and Home Care Maintenance cream, to Lumixyl, to something containing some prescribed Hydroquinone, to a product that is perhaps going to work more slowly but is more affordable, such as Nimue’s day and night fader. You should also consider some treatments, such as Limelight (which is a type of laser).