It's hard to know what would help without knowing the specific cause, but there are some comparatively-likely things to check: diet, micronutrients, exercise, sleep, and amount of social interaction. If any of these have changed recently, try changing them back. There is at least one blood test I'm aware of that should have be done (thyroid). You also might go back and ask your doctor for a different antidepressant without or with different side effects.