This information is from helpguide.org and are the major signs of depression. If you feel any of these or all of them, that you must seek help to retain your physical well being, and your mental health:

Are you depressed?

If you identify with several of the following signs and symptoms, and they just won’t go away, you may be suffering from clinical depression.

* you can’t sleep or you sleep too much
* you can’t concentrate or find that previously easy tasks are now difficult
* you feel hopeless and helpless
* you can’t control your negative thoughts, no matter how much you try
* you have lost your appetite or you can’t stop eating
* you are much more irritable and short-tempered than usual
* you have thoughts that life is not worth living (Seek help immediately if this is the case)

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Depression is different from sadness. Occasional sadness happens to us all and can last for awhile. Depression is a sadness that affects your life. You feel hopeless and empty and don't want to even get out of bed because you always feel exhausted. It kind of has a way of taking over your life and find it exhausting just to get through the day. You don't find things fun that you used to like doing and you start to pull away from friends and family and spending time alone. Stress can seem like depression so I would go to a therapist if you think it might be depression.

Depression which is also known as major depressive disorder can be a challenging disorder to face and can come with many different stages of symptoms. The symptoms can range from depressed moods such as increase crying, sadness, moody behaviors and increase sleepiness or sleepless. Significant increase of interest of activities that used to be pleasure to you. You will also see a dramatic change in your weight (gain or loss weight) and you can also lose your energy. You can also start to feel that you are worthless or inappropriate guilt. The best advice/answer that I can give you is seek medical attention and I will also provide a article on depression as a whole.

I hope this article and information that I provided will help you.
http://www.webmd.com/depression/default.htm