Crying and nightmares

Hi, welcome to the ehealth forum and I am glad to help you.
You seem concerned by the feeling of sadness and emptiness most times of the day with episodes of crying. You have history of cutting yourself in the past. A change in eating habits, loss of sleep, recent falling out with your father and two best friends has also been mentioned by you. This difficulty in social adjustment has led to social isolation. You also made a mention of being happy sometimes as well.
From your description, you might be suffering from depression the exact nature of which can only be determined by your physician after a detailed history and investigations to rule out any drug effect or hypothyroidism etc. You cannot take it like that people feel the same and there is nothing abnormal. You must seek the help of your doctor for prompt diagnosis and management. You might need antidepressant medications and cognitive behavioral therapy and interpesonal therapies may be helpful as well.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.