I got the word that I was searching for earlier: costochondritis.
Hi there,
It is good that you've had the CT scan done and that it was normal - that cancels a lot of other possibilities out - for eg. Gallstones. I don't think that you would be able to reproduce that particular pain, if it was caused by GERD by flexing and moving. I would think that it can be muscle related?
Have you tried taking anti-inflammatory pain killers?