Dermatologist is definitely the right way to go. They'll end up giving you a shot at the worst, and most likely some creams, face wash, pills, etc..
I've heard good about Poseidon, but from what people have said in this thread, it's hit or miss. If you'd like, give a try. Not to pimp too hard here, but it's been improving skin quality in many users who've tried it and logged with us. I've used it and it also helped to clear things up a bit. If nothing else, it wouldn't hurt.
Just be sure to keep clean, don't use too hard astringents when washing up, and make sure your diet is healthy. Oh, and wash your hands! That's always a good idea.