I've been going through something similar over the last several months. I work for myself and I've been laying down to sleep in the middle of the day. But that low energy was also accompanied by a sense of dread to do anything, no joy... and fleeing suicidal thoughs. So... I'm obviously depressed. Last week I was told to double my Wellbutrin (stimulant).. which has halted the sleeping... but not the lack of joy, dread and those fleeting thoughts. When this episode started I might explain it as you do.. just low energy.