I'm Suffering from Facial Pigmentation for 4years

there is ashy coloration of my face and hands.it is non itchy,non burning.it seems agravate on sun exposure.some times there r raised border around the pigmentation,which disapper automatically.i did 3 biopsy,2 says nothing contributory,1 says ashy dermatosis.physcian advised no treatment in bangladesh.some advised to apply sunscreen lotion,but no improvement.i think my disease is not diagnosed properly.what can i do now?pls help me.Saiful,dhaka, Bangladesh.