Chest pains

So exactly a week ago today I had my surgery and feel I am healing very well, each day making more and more progress. I am able to walk progressively farther each day, take less pain Meds each day etc... However I have had this semi- continuous chest pain on my left side near my heart. Slightly above it but still a couple inches below my collar bone. It is at its worst when I lay flat, km pretty convinced its just gas. But it definitely has my attention. Sometimes making it difficult to breathe. I called my doc and was told to keep taking deep breaths, keep walking, make yourself cough occasionally, keep up in Meds etc. I've been doing all that and the pain is still there, any suggestions? Or something to help?