What am I doing wrong? Acne?

I had a problem with acne since I was 12!! I'm 15 now and I went to the dermotologist an they perscribed me with benzoyal peroxide 5% and differen 3% and this lotion that start with a C but it's a medication and with in a week I saw results but your face does get a little dry but it's worth is in the end ask him for that