There are multiple causes for facial hyperpigmentation. Sun tan, overweight, pigmentation disorders like acanthosis nigricans or melasma, lichen planus pigmentosus, rhiel's melasnosis, 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. Get an online consult or meet a dermatologist directly for a proper evaluation of the condition. Hope this was helpful.