I had fairly significant back pain pre-op. I wasn't particularly large chested, but binding combined with the kind of work I was doing and everything that came with it gave me a lot of chronic pain.
After I recovered from surgery, the pain was better. My posture had improved a lot, which I think was contributing to the pain. I have fibromyalgia, so I'll probably never be totally pain free, but it's much better now than it was before. I still want to see a chiropractor to see if there's any underlying issues that could be resolved, but if there aren't, where I'm at now in terms of pain is very manageable.