My son has painful acne on his back. He has acne on his chest and face, but his back is the most painful. He can't even bench press some days because he can't take the pressure on the pimples.
He's tried every type of oral antibiotics with no success. He's used topical creams (duac, tazerak) that did nothing. We even have a red blue light, but honestly can't say that it "wouldn't" have helped, he never used it consistently.
He now takes accutane. On week two and sees some improvement. Had some issues with an initial breakout that lasted two days, swollen lips, sore nose, more pimples on face and back. Those are clearing up now and he doesn't feel like crap anymore either. He was very tired in beginning. So I would say, if you haven't tried working with a derm, then maybe you should get the opinion of one.