Please don't self treat, facewash has negligible value for pigmentation. The more  you scrub, the more darker it will get. Therebe several causes why your skin would turn dark or you may get pigmentation. Sun tan, overweight, pigmentation disorders like acanthosis nigricans or melasma, nutritional deficiency etc are some conditions. Unless someone examines you, we cannot know the cause. Unless we find out the cause it is difficult and pointless to treat. Please call me or send photos with detailed history using online consult option for examination and proper treatment.