So I'm 24 and have had these problems since I was 13 talk about along time of having to deal with these cysts I used to suffer with acne aswell but when I hit about 23 they calmed down dramatically it was only today that the doctor I see in a&e actually sat down n took notice everyone else kept fobbin me off with other tablets that never worked and also the doctor in a&e suggested I take a lactose diet no milk based products for 6 weeks for the first week I'm on flucloxacillin and co-amoxiclav that intense course of medication I will then be on minomycin I really hope this works il be a different man after 
Best of luck to you on your new regime, i really hope it works for you and you see a difference, i know how hard it is and i feel for you having it for such a long time, you now might get the results you've been after. I think it's always best when someone takes the time to sit down with you and talk to you instead of just prescribing you something and moving you on for another few months, so it's good that someone did
Keep at it! If you see a break out don't worry, normally when trying new medication you get a break out, but I guess you know this as you've tried past medications! Also the diet could make a difference as well, it's good that your doctor told you do that, like you said you don't want brushing aside so see how it goes then if you don't see nothing go back again and don't give up!
It is fantastic when you meet a professional who is willing to work with you. Like, actually work WITH you. That can make all the difference in our hopes in struggling with acne. We have a prescription med forum if you'd like to poke around there, too. http://www.acne.org/messageboard/index.php/forum/4-prescription-acne-medications/ Please keep us posted on how this goes for you!