Now, don't panic...

[pegkerr]

But I'm at the hospital ER being evaluated for chest pain. The nice paramedics came to our home and hooked me up to the EKG machine and said my heart was normal. Lungs are clear (i.e., not pneumonia).

***
Just saw doctor. Given EKG, and answers to questions I gave him, he thinks this is muscular skeletal: nerves and muscles run between the ribs, and sometimes they just act up. They'll do a chest X-ray and blood tests to be sure.