Hi Ruby, Costochondritis starts in the middle of the sternum. It radiates (mostly) down the left arm and up into the neck. I have had that pain that you describe, well similar, and it went from the underside of my shoulder blade into my ribs and down the left side of my back. It is touchy painful skin, but also in the muscle, the test for cartilege inflamation is to gently press one of the ribs in that area if it hurts, then its cartilege (can't spell anymore) and the relief of the pain and reduction of inflammation is from neurophen, or ibuprophen. A NSAID. It can take quite a few months to go down.
its not called costochondritis if its in the middle of your ribs!.. can't remember what my doctor said it was called.
hugs

http://www.emedicinehealth.com/costochondritis/article_em.htm

Sounds like its nerve related. I have a general burning pain in my shoulders and back and neck that is really painful right now. Starting to think it could be the fibro flaring up.

I have that, 'Cept on my Left side..Thru the Blade, Breast, Shoulder..sometimes Dull, Achy, Sometimes Sharp Pains...mine is Not Costochondritis...mine is caused from Severe Arthritis in my C & T Spine. Will Hopefully come up with a Plan to Treat it, so far my Chiro has been a MAJOR Symptom reliever..

I was also getting pains IN my left arm..been havin this now since January...have had alot of Tests..no Heart issues...thankfully. I have had very Little Discomfort since I have been seeing my Chiro, took a few Visits to get everything back where it is supposed to be and the Muscles to STOP spasming..inflammation down, which must have been pressing on the Nerves..I been doing the exercises he gave me FAITHFULLY...simple movements with Deep Breathing to Fully Expand everything..

I Hope you Find your Answers !!

Could me myofascial pain. A lot of costo pain is really myofascial and can be relieved by massaging the offending trigger points. I have absolutely tons of TPs in that area and am sure I could get a doctor to diagnose me with costo, but why, when I can control the pain with TP massage??

Kind of funny because as I was scrolling through the discussion treads, I was rubbing my right shoulder with a hot pad on my mid back. I just blame everything on the fibro. It is what it is. Massage is very effective for me with neck and back pain. It has to be a deep tissue massage, though, not a foo foo massage. Sometimes it's better to schedule a half massage, two or three weeks in a row. That usually does the trick.

Oh yes, it most likely is constochrondritis. I have had flare ups many times, and sometimes the pain can go into your chest cavity as well. It is horrible. take an anti- inflammatory, it does not take the pain completely away but it can help. take care and hang in there

Don't forget that gallstones can also cause pain in that same area. If you're having any sort of digestive upset I'd be sure to get it checked out.

Hugs, Susan

sounds like gallbladder maybe