Weird excruciating pain below my left side armpit

Hi All,

Not sure what's going on, but from time to time, I have this excruciating pain, the kind of pain that make you want to call 911 happens to me.  First I would feel stiffness on my center left side-chest, then the pain would starts. I've pinpointed to be under my armpit and to the left of my nipple, on the left side. The pain is unbearable, if I was sitting or standing, the pain will just grow stronger, I have to lay down then it will slowly go away, but the pain would still be there for days but just subtle. It has happened twice to me, and I was not doing any in particular, just going about regular life.  The last time it happened was about 2-3 yrs ago, and it just happened last week to me.  Prior to the last episode, now I have constant subtle pain in my lower left rib cage, sometime the pain would become noticeable,  but pressure would applied on me, I can feel the pain, not sure if anything related to the excruciating pain that I’ve been experienced.

I have CT scan and x-ray done, and it’s shown that structurally everything looks good.  So my doctor just blame it to the acid reflux,  but if that’s the case, then I would have the kind of excruciating pain  more often due to the acid reflux but I am not, therefore it’s very weird to me.

Much appreciated if anyone can help.