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

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