As dr. Nash mentioned, you may be suffering from depression
if you have a certain combination of depressive symptoms.
You can do some some self rating for depression to "check' if you might have it. Zung depression scale is one of the questionnaires you can use. Healthnet.Umassmed.Edu/mhealth/zungselfrateddepressionscale.Pdf
if you believe you have depression, see your pcp or a psychiatrist.