My Husband Has Been Sick For 5 Months With Chronic

My husband has been sick for 5 months with chronic fatigue, no appetite, overall weakness, shortness of breath. He has been to Vanderbilt to see a cardiologist, blood cancer doctor, GI doctor and an infectious disease doctor. He has also gone to a holistic doctor for supplements and IV treatments. He continues to have these issues. Every body shakes their heads and says "i don't know".