1) change your diet and eat about 2x the amount of vegatables as you think you need. Stop eating processed foods. Eat real food.
2) one hour of walking a day and make sure your get sun rays
3) if you drink alot of milk consider not drinking milk.
After 2 weeks of this you should start to feel better. Continueing with this behavior will keep the black dog away.
If you do not start feeling better then you should talk to your Dr.