Hey I feel for you. I had acne until I went on the pill, then I had amazing skin and couldn't get enough compliments. So for me it seemed that hormones were a problem. However when I went off the pill what helped was to simplify what you put on your skin, and that includes hair care products. Often people forget that shampoo and conditioner contain harsh chemicals and all commercial products are harsh. Whenever I used to wash my hair with Pantene, herbal essence etc I used to get a redness and bumpiness along my hairline and this is where trouble areas persist. I didn't realise until a few years ago what was the culprit. When I tried the no poo experiment (abstaining from use of shampoo and conditioner) I had clear skin. I now use A'kin which is an Austrlian brand that is completely organic and naturally derived (all ingredients on the back are accounted for), and it has been gentle on my skin.
So although hormonal problems contributed to my skin problem, my skin was made sensitive and by using commercial face washes and shampoos and conditioners my skin was constantly aggravated.
I tried benzyl peroxide in the past and they can dry things out quickly though it causes dry skin, fine lines and wrinkles and make you very susceptible to sun damage. I also don't want to put harsh chemicals on my skin and that includes bp (NOT British Petroleum!)
It could be any set of factors that cause your skin to flare up - hormonal imbalance, constant stress, senstive skin, sensitivity to hormones, over active oil glands, too much washing and aggravating of skin, constrictive clothing and too much bedding at night (especially suspect if affected areas are chest and back). You can try and rule out different things which you think may cause your acne to see if it makes a difference. This can be from drinking a lot of water in a 2 week period, to changing your bedding every week.
Also the rubbish they spew about how there is no scientific proof that food can cause acne, that's not true. My personal experience says otherwise - if I eat chocolate, sugary food and drinks and too much fried foods and alcohol, I get spots instantly. Other people have had the same experience.