How To Get Rid Of Dark Spots On Face, Back Area And Thighs?

Hi doctor, i am 19 years and i have some problems of dark spots on my face as well as on my different bodyparts like hand,backside,thigh. What remedies should i use to cure it?? Please help me . And it is also from last 4years . No medicine worked except omela and cosmelite on face. But it worked once after that again dark spots appeared .