How To Get Rid Of Hyperpigmentation All Over The Face?

i am 22 yr old male i have serious hiper-pigmentation problem..... my face seems much dark than rest of my body . When i avoid direct sunrays for weeks then it comes to normal complexion. But when i roam about in sun for even an hour it gets dark . The main problem area is my face and that too on forehead. . it becomes literally black. But my whole body complexion is wheatish and somewhere fair. I looks odd and embarrising too . What should i do ?