It sounds like you have tried all the conventional things to treat this but have you tried making changes to your diet? The reason I ask is that my wife had a similar experience as a teenager and she was vegetarian and through my own 'health journey' the last few years I've educated myself on aspects of diet that can have quite profound effects on your body (and mind). For instance, who would have thought that I could have cured my asthma, rhinitis, colitis, tremors and arthritic pains simply by omitting wheat from my diet? Have you heard of Dr. Shawn Baker? Google 'Meatrx' and you will find many stories of how people have resolved their health problems, including one man's acne clearing in just one week. I know that must sound unbelievable to you after everything you've tried and been told but its worth a shot.

BTW, you did nothing wrong, just like my wife didn't and I didn't. Some people are genetically susceptible to certain things (some people can get skin cancer just from mere minutes in the sun). If you've tried everything else, then you should definitely try changes to your diet. You have nothing to lose by doing it and everything to gain.