Sunshine.
Exercise.
Faking it.
Seriously, sometimes I can pull myself out of a slump by faking it...I'll just "pretend" that I'm feeling good and then force myself to get up and do something, and I'll find that it actually works! I DO feel better! It might not be immediate, it might take a few days of small spurts of activity, but it could help.
You said you were sick...could you be anemic? Pay attention to your diet, focus on good nutrients and hydration for a few days and see if that helps. Take your prenatals