How can I clear my acne quickly?

I used to have extremely bad acne, then I went to the doctor. He described me Tetracycline, which seemed to work perfectly fine, and the acne face wash called Oxy that you can buy at any story. It all worked fine, but now my acne is showing up again. It comes on my chin, forehead, and cheek (only one). My cheeks are dry and I use face moisturizer; my chin and forehead though are normal. I really need this acne gone fast. Plus I have sensitive skin. I only use mineral powder foundation. What can I buy (preferably at walmart) to help my skin???