Has the reality of working from home been different from what you imagined? If so, you may be experiencing symptoms of burnout.
People who have bipolar disorder can have periods in which they feel overly happy and energized and other periods of feeling very sad, hopeless, and sluggish. In between those periods, they usually feel normal. You can think of the highs and the lows as two "poles" of mood, which is why it's called "bipolar" disorder.