What Are The Light Brown Spots Spreading All Over The Body?

i am 28 yr old,from my childhood i am having light brown spots on legs but for the past 1 yr its getting dark and spreading through out my body.Now the spots in legs area are so dark brown and the starting dots are so light.i have noticed these dots are in each hair starting points in the skin .i consult a doctor he said its because of shaving but i never did shaving on chest area and other parts.i used to do only on legs.so please help me what kind of dots these are and why it is spreading and what kind of treatment helps.