Do you have a good diet? If you eat/drink food that contains a lot of sugar, then it can cause an acne outburst. I was also told that caffeine and alcohol can also cause acne, which I experienced; no more alcoholic energy drinks for me.
You should also wash acne with warm water using a face/body wash that contains alkaline level of ph5.5.
I don't know anything about the stuff you can buy off the shelf, except that you should look for something that contains at least 5% benzoyl peroxide.
You could also see your doctor and ask for antibiotics. It worked well for me, but now I learnt that some people have experienced hearing loss due to antibiotics.
Alternatively, if you want instant results, you can try the mother of all medicines - Roaccutane, which is a prescription medicine from your dermatologist. As with all prescription medicine, you may experience side effects, which vary from dried skin to hallucinations (which is rare). Some people also say that Roaccutane has also contributed to depression and suicide, which are also rare.