The symptoms you've described - fatigue, not being able to sleep, sadness and thoughts of wanting to die - are all possible symptoms of depression. Other possible symptoms of depression include a loss of interest in things previously enjoyed, weight gain or loss, restlessness, feeling slowed down, feelings of guilt or worthlessness and difficulty thinking or concentrating. However, it is impossible for me to tell you for certain what is wrong with you so it would be a good idea to get a check up from your family doctor. There are several medical conditions, for example hypothyroidism, which can mimic the symptoms of depression. Once these conditions are ruled out, your doctor will be able to either treat you for depression or refer you to a psychiatrist or therapist who can help you.
If you would like to learn more about the symptoms of depression I would recommend taking our free depression symptoms screening test to see which depression symptoms apply to you.