Wow ,

It sure sounds like costco, I have it from the side to the front of my chest. But make sure there was no rash in the area as that would lead me to think shingles. But as long as you have ruled out the heart that's good.....

I am also a fibro sufferer and have these kinds of pain often, sometimes they are unbearable. nasaids, anti inflammatory, muscle relaxants, do help so does heat...

Sorry your in so much pain