Hi I Have Very Bad Acne On Both Sides Of

Hi I have very bad acne on both sides of my cheeks, no where else, and on my chin the bumps on my chin go away within a week but the ones on my cheeks have been there forever!!!!!! They won't go away, they are really small and hard flesh colored bumps you can only see them when I'm in light.. Why won't they go away? What can I use? What is causing this acne? Help please!!!!