How would i have portal hypertensive gastropathy when all blood work and ct scans are perfect?

Who made the dx?: Ask whoever made that diagnosis. He/she may have the explanation

It is what it is: I am going to assume you were found to have portal hypertension and that the endoscopic / clinical picture matches what we know of this uncommon entity. Anything from Budd-Chiari portal vein occlusion to central hyaline sclerosis to a variety of other liver problems causing portal hypertension may be the explanation. These do not affect bloodwork. Ask for 2nd opinion if you're not fully satisfied.