I had something similar last year. I was having sharp pains in my chest and under my arm. I finally went to my PCP and he found a knot in my breast bone. I had Costochondritis. It is something that can last for 4 months my doctor said. Ibprofen for swelling or Tylenol for pain and a heating pad or hot baths really helped me. This was back in Sept. I haven't had major pain since December. Every now and then I get a flare up but nothing like I was having. Try a heating pad or try a nice hot bath. Good luck! Hopefully you will feel better soon!
Have they ever considered this as possibly a musculoskeletal problem Costochondritis and other things can cause awful pain in the ribs, but I don't know of have heart if it shows up on a cat scan. I suggest you get a new doctor if you haven't already. Also you deserve relief from pain until they can find out what is going on, so try to get into a pain management clinic. If your heart has been checked out and the cat scans are fine, they could run an MRI. Have they checked your bloodwork thoroughly. One more thought, a rheumatologist might be able to order some of the tests you need. Hope you feel better soon, I am so sorry you are in pain