My friend had really bad back and chest acne, for YEARS, and it wasn't until just recently they found out it was caused by a wheat allergy. I also had face acne, and birth control really helped! I eventually got moved to Accutane, which is some seriously heavy duty stuff, but has made a world a difference!
You need to go to a dermatologist and ask for isotretinoin treatment. In the mean time. Start including raw carrots everyday in your diet, and avoid chocolate, rise and egg yolks.