Sharp pain in left side of stomach

Hi everyone! I have a question that I can't find a solid answer for on google. Ever since my anxiety first spiked when I was 11 and I stopped eating as much, when I am very stressed, do too much physical exercise, or sometimes when I eat greasy food, I get a sharp pain in the left side of my stomach just below my ribcage. Heat seems to help somewhat but only time can make it go away. It's been a consistent symptom of mine for over a decade and it worries me but no one can tell me what it is. Any insight would be greatly appreciated.