I had similar pain for months and all my tests came back normal. They did lab tests and radiology imaging CT scan. Everything was normal. The pain finally went away in about four months and then came back in a few months and then again did more testing, and nobody could discover anything wrong. I noticed when stop exercising completely and just rest the pain eventually goes away, but it usually takes a long while for it to go away, sometimes up to a few months, so I think in my case, it might be muscle related even though it feels like it’s under the rib cage on the right side.