Does it feel weird in your back? Cause, I've had this weird feeling when I breathe too..but mine is like at the bottom of my collar bone, in the front and also kind of involves my shoulder. It's like I can't breathe in deep because of this weird stabby pain in that area.
I am currently going the the Lung Ca scare too, among others.
With the rod in your back, you are probably right about that causing your pain. Have you been hunched over at the computer more than normal latley? It may be a posture issue.