What Causes Twitching And Burning Under The Left Ribcage?

I am 33 .173 ..I have bad pain under my left ribcage it twitches and burns but I am in a lot of pain...I get no relief unless I take tramadol or Tylenol 3 ...I have constipation and have lost a lot of weight...been to er aand they gave me things to gas which do not work,,,,what might this be and what test to ask for blood work came back with proteins and im anemic