Why is my skin breaking out all of the sudden?

I am 19, almost 20, and as a teen I never really had a problem with acne. But all of the sudden my face start breaking out like crazy, all over- my cheeks, chin, forehead. I eat pretty healthy and really limit my dairy. I workout and wash my face morning and night but nothing works. I went to the derm and got some atralin gel and some cindamycilin lotion along with a pill to help and I have been on it for a month with little to no change. my acne is small with a few large painful ones occasionally. why is this happening to me? what can i do to really get rid of it fast? thanks