What Causes Dark Pigmentation Patches On Both Sides Of The Cheeks?

hi i am 20 years old girl and i have got dark pigmentation patches on both sides of my cheeks and plus tanned skin , all due to 3 hours bus jhourney everyday and sun and pollution...plus i get a very dry skin in winters and normal skin in summers....i have got minor pimples too after my this schdeule of travelling everyday..i have tried adapalene for pimples and i have taken a topical medication for the patches and its been 1 year for dese ugly patches and tanned skin and i could not get over it til now...please suggest me..what to do..??? waiting for the reply