I ran across this really great video explaining how you might be able to tell what is contributing to your acne. More or less, it's acne mapping - where the acne that occurs on your face corresponds to a something that might be happening in your body...such as kidneys, digestion and hormone fluctuations. 

I knew breaking out on your chin usually signals hormonal acne, but I had no idea about the others. It totally makes sense and is a good place to start if you aren't sure what is causing breakouts!!