I am also a sufferer of chronic costochrondritis. It is the chief area my fibro attacks and believe me I know what you are talking about. I happened to see my rheumatologist just yesterday and he declares it is very common in fibro. Actually when my chest ceases to hurt it shocks me and doesn't stay gone for long. Now I only take Advil, have never added other drugs and pray I can remain this way.
I actually rub (lightly) a product with capsicum and it gives me good relief. My sternum muscles feel as though they are under siege and this helps. Also a nice warm heating pad across the chest does wonders.
Hope this helps to know you are not alone.