The lethargy was eatin' me up too, Lew....a combination of a symptom of depression and a symptom of low testosterone. Talked to medical folks, got fixed up, and now I'm much more energetic. But it all started in a very similar way for me, Lew.
You could summon up some of that defiance you surely have, and stare down that lethargy thing.....see what your doctor says.