My name is Jerry. I am 59 years old and experience this stabbing pain two are three times a week now. Started getting these pains under my left nipple and under the rib cage eighteen years ago that were made unbearable with deep breaths lasting from thirty to forty minutes. At first they were only on occasion but have become a way of life for me. It feels like a knife stabbing my heart. So many times I thought it was a heart attack and I found myself in a panic with my heart racing. I found out early on that if I were to chew and swallow six to eight tums and one gasX the pain would be gone in ten to fifteen minutes in most cases. I have had many doctor visits and my doctor does not know what it is.  When in the panic mode I would head off to the ER but these visits would yeild the same answers... doctors saying " it must be muscular or skeletal pains because your heart seems fine" after an EKG is normal. All I can say is Bull crap!!! It is not simply muscular or skeletal pains. It is something else.....some kind of trapped gas or something. I have had a Colonoscopy performed on three occasions and a Endoscopy performed on two occasions. That Doctor said each time that he only saw some redness. I am furious and ready to have my chest ripped oven to see what the heck is causing this problem. I have taken antibiotics that the doctor said were for the bacteria that causes ulcers. I have taken Parasillan to cleanse my body of possible parasites. I just want the pain to go away so I can finish my life without the stabbing pain. Anacids and Anti Gas meds help so it has to be due to acid or gas that is getting into my chest somehow. So my friend I do know exactly what you are describing and it is an awful pain to live with. I hope you have better luck than I have had thus far finding an answer to this problem.