Anyone ever think of this?

Chosticondritis is what it's called when it affect muscles in our chest wall. It can affect breathing.
As far as affecting our breathing, I tend to believe that fibromyalgia is a nerve issue rather than muscle. Which means only certain nerves are working to cause the spasms. If you think about, that's why the have the point test for fibro. Certain areas are very common among fibromites. It could also explain why our pain's aren't the same and why so many other things can be affected.
Anyway, that's just my 2 cents from what I've read and experienced and gotten out of my drs. I think it's interesting to discuss because right now it is kind of a "trash can" disease. Meaning that someone with fibro could have something else altogether going on but because they have fibro their dr is going to write it off to fibro. That's why you really have advocate for your own health.

I get a lot of chest pain (chosticondritis + asthma + fibro).
I can tell you which ones playing up because they all hurt differently. Chosticondrist is sharp, fibro aches, and asthma is like a sledge hammer hitting my back.

One CAN set off the other, stress is a big trigger for asthma, and breathing differently because it hurts to breathe normally will also set it off.
If your pain impacts on your breathing at all, you should talk to your doctor about it.

The one thing I have found helpful with my breathing (during pain flairs or an asthma attack) is to actually envisage what’s happening when you breathe.
When you’re breathing right you’re not actually actively sucking air in. Your diaphragm is working like an accordion. The diaphragm compresses down, pushing your organs down, which creates space in your chest cavity. This creates a negative pressure in your chest, which air rushes to fill. Then the diaphragm releases, and the organs press up creating a pressure which forces out the air.
If the diaphragm can’t take the load (or your bronchi have swollen and made the air exchange require more force) your rib/stomach/back/shoulder muscles all get in on the act.

Pausing to interlace your fingers over your diaphragm and focusing on using your diaphragm to separate them is usually enough for me to let go of all the other forced breathing I’m doing.

(I mentioned all the stuff about accordions because I never really had any success with this exercise until I learnt the whole “breathing is just negative air pressure,” thing while studying the anatomy behind yoga.)