You are having depressive disorder.
There is generally no specific root cause of this depression disorder. it is now believed to be a physical problem due to lack of serotonin in the brain.
You should consult a psychiatrist for this. Psychological diseases are as much diseases as physical diseases. We need to get them treated as matter of factly as we treat a physical disease. There are a wide range of antidepressant drugs which will no doubt help you to regain control of your life.If you cannot get a direct appointment with a psychiatrist, you should show your Primary Doctor or your GP. If necessary your GP or Primary will refer you to a psychiatrist.
Dont try to deal with this alone. Get help, show your doctor. Depression is a very common medical condition in the modern age, and you must deal with this medically. A very large number of people suffer from this and have been able to find help through medicines and counselling which your doctor can prescribe for you.
If you do not have a doctor or a psychiatrist, you need to google 'psychiatrist near me' to see a list of practices, and then choose one and call and make an appointment.
Some steps you can take for now are:
Lots of fluids - water, juice, Gatorade.
Vt. C, Zinc and Vitamin B complex supplements -you can get this at your pharmacy.
Regular exercise - take 30 minutes of walk 5 times a week at the minimum. This is the most important step.
Maintain optimal weight – check your BMI on the net, its easily done. If you are overweight, try to reduce weight by at least 5 pounds, this will help greatly.
Avoid smoking, cut down on alcohol, cut down on caffeine
Regular hours of sleep - this is most important.
I would like you to try Yoga. Yoga can give great benefits in depression and anxiety - probably the best natural treatment for this. Join a good yoga class - it will surely lessen your symptoms.
Also try to break the mold. Join a new class - perhaps a music class. Join a club. Dont sit at home in the evenings - go for a cinema or a pub, etc. Dont settle down, move around - this can work wonders.
These steps will help, but you should consult your doctor or a psychiatrist at the earliest for this.