Hi Dave: I want to follow-up on what Danny G. and Erik said about exercise. Exercise is an excellent antidote to depression. I know this from personal experience. If you can get yourself up and out and doing something (walking, swimming, biking), it will help tremendously with depression.
However, If you find yourself lying in bed (or on the couch in a fetal position), or at least unable to leave the house, then you need to get to a doctor to get antidepressants. Good luck! Candace