I have been using melacare cream for 4 years. Now I have stopped it but my skin became very dark. What can I do?

please post photos. melacare shouldnt be used for years this Is likely damaging your skin and you will need a cosmealn peel, aerolase laser, and propoer skin care with growthfactors and stem cells to repair the damage. you need complete sun avoidence and protection.
Hyperpigmentation from any type needs a combination approach of peels like cosmelan,  lasers like clear and brilliant and aerolase or laser genesis, radiofrequency like venus viva, and constant skin care and sun protection.  Bimontly facials with silk peel dermalinfusion is essential to hydrate, exfoliate and infuse vitamins and antioxidants into the skin.  If you have acne you can do additional treatments and peels to get more improvement.  I suggest a formal consultation with an expert in lasers and peels. Best, Dr. Emer.