Xrays, urine sample, and blood work any ideas ?

so i recently got an xray of my stomach and got blood work done and also they took urine sample. all came back fine, but im not fine im still having bad stomach and back pain, nausea, and no apetite. what all do they check for in blood work? xrays? and urine samples? y could they not fig out what was wrong? especially with blood work? they said my blood work was fine, does that mean nothing is wrong with me?