Lately, I've been having a chest ache, either when I'm laying down or walking certain distances. I'm starting to feel the ache in my back as well.

Differential list of. possibilities is huge & few clues were offered. Medicine is not about "all knowing knowledge" or any certainty; issues far too complex. Medicine about huge basic information, theories, strategies, detective work, educated guesses, tests of strategies applied, evaluating the results of the theories & strategies chosen & implemented (to what quantitative degrees) compared with other ongoing issues.