I googled anemia.

It may be "slow chronic blood loss" from your ulcer and esophagus problems, which i understand to be ongoing? I mean, you say your GI issues are good for a few days, then you get sick again. I think that means they continue to be a problem. Like ripping a scab off a wound - its not healing? Malaise is a common symptom of anemia.

Yeah if i were you, i would ask what the cause of the anemia - usually its some bleeding, but i guess it could be something else.