I have costo as well, it has really improved over the years, although I have learned that I just can NOT lift anything or basically use my chest muscles in any way, shape or form.
It sucks but atleast it keeps the pain away most of the time.
I also have a heart condition, so I can maybe help you clear up some of your concerns.
What heart tests have you had done? Do you have a family history of heart trouble?
Heart pain is usually not the kind of pain that you can point to, its more like a crushing(elephant on your chest) type of pain. Also, with costo the chest/ribs are usually tender(sometimes extremely). Tenderness is not usually indicative of heart problems.
Anti-inflammatories are usually suggested. Are you on an anti inflammatory?
The best advice from my own experience is to avoid using your chest muscles--I know it is hard especially when you have young children, I have been there, my youngest is 4. I have had costo now for about 9-10 yrs. When I am really suffering a warm bath will usually help.
Feel free to ask any questions you may have. Rest assured if they have given your heart a good check, then the cause is the costo...and sometimes anxiety.
Anxiety can give you all the symptoms you fear the most.