My boyfriend had a stomach ulcer not that long ago and now he has blood in stool and after working all day there was blood residue on his boxers?

Blood From Ulcer?: Your boyfriend should see his GI physician. The source of the blood needs to be discovered. Most bleeding ulcers resolve with medical therapy but recurrent GI bleeding requires repeat upper endoscopy.. Also, this bleeding may be totally unrelated to his prior ulcer and may require colonoscopy if the upper endoscopy is normal.

See Doctor: Ulcers can only be diagnosed by an endoscopy and should heal in a few months with medication. Dark blood in stool could indicate that the ulcer is bleeding. Bright red blood in stool could indicate colon cancer, inflammatory bowel diseases (ex crohns or ulcerated colitis) or medical problems. See a doctor immediately to determine the source of the bleeding.