What am I missing?

I'm a relatively new nurse so I know I'm missing something. My dad has a hgb 10.6, he said his iron was really low but didn't ask exactly what it was. I only got the hgb level but bugging him. He has lost 10lbs over the summer but thought it was because he had been working outside a lot. He is weak, lightheaded, doe, and has palpitations after coming up 1 flight of stairs. He just turned 50 a month ago and is in relatively good shape with no PMH other than asthma. His father died of pulmonary fibrosis almost 2 years ago, he was diagnosed and died the same week. His grandfather and several uncles have had colon cancer. At the MD office his o2 sat was 98% after walking around the exterior of the building. Urine was good. The MD wanted 3 days of stool specimen to test for blood--which was negative. He said his stool stinks, he is nauseous, and at times his stomach hurts. Last night he ate spaghetti for dinner and was up all night with indigestion but didn't call me. I did finally talk him into going to see a doctor for an EGD, colonoscopy--he sees her tomorrow. All his family md did was tell him to have it done (after I already told him to schedule it) and call in some iron pills. He is under a lot of stress at work but never had an ulcer before. The only surgery he has ever had was spine surgery to remove a broken disc which was probably 15 years ago. What am I missing? I want to think its an ulcer but I know it could very well be colon or stomach cancer.