You definitely sound ill and need a thorough workup for malabsorption syndromes, diabetes, hyperthyroidism, vitamin deficiencies, etc . and I would stop donating blood until you get a diagnosis and treatment for what ails you. It seems a gastroenterologist would be your best bet as far as specialists beyond a primary care doctor. I hope you have insurance and can get better food intake. You might want to reread my previous posts to you about your situation.