What Causes Lighter, Irregular Patches Of Skin On Body?

Hi Docs! My name is Josh. Am 19, 5ft 10inch tall and a black guy. I noticed lighter irregular patches of my skin more like eczema but its not. This lighter patches are shinny and very pale when i sweat. Its allover my back, shoulders, chest and spreading downwards towards my extremities. My face is almost totally covered making me look lighter in complextion but pale when I sweat. I'll really appreciate if any Doctor could help me. Thanks.