My 76 Yr Old Husband Had A Successful Complete Knee

My 76 yr old husband had a successful complete knee replacement 2-1/2 months ago & happily recovered very well. However, about 6 weeks ago he started feeling weak, had chills & hot flashes frequently, lost his appetite and 25 lbs, is depressed each morning when he realizes he feels no better. Until this problem, he was very active mentally & physically. Now he sleeps most of the day and night. . First his primary doc prescribed an anti depressant. A Urologist ruled out a UTI or any other urological problems. His orthopedic doctor is puzzled. His gastrointestinal doc had an ultra sound of liver, gall bladder & pancreas then performed an endoscopy. No problems showed up. I took him to the emergency room when he was feeling faint and there he received brain scans, & a multitude of other tests. He was discharged saying he has no life threatening problems. Please advise.