There are many reasons why your skin would turn dark. Sun tan, overweight, pigmentation disorders like acanthosis or melasma, nutritional deficiency etc are some conditions. Unless someone examines you, we cannot know the cause. Unless we find out the cause it is difficult and pointless to treat. Please call me and visit my clinic or send photos with detailed history using online consult option for proper treatment. Donot use steroid containing creams like melacare or skinlite or Panderm or betnovate etc, it causes serious side effects.