I think your symptoms are quite concerning and warrant immediate evaluation by a psychiatrist
. You have listed many symptoms, and collectively they cannot be assigned a certain condition with the limited information that we have. This is especially true because of your age as some of the conditions that you might have are typically not diagnosed in someone as young as you are. For example, the symptoms of hearing things that are not there and feeling that you are being watched by others are common symptoms of schizophrenia
. These feelings in combination with depression
can be a sign of a related disorder called schizoaffective disorder. The other symptoms that you have such as having few close friends, not feeling like you are inside your body, and feeling like the people around you are just imaginary are all symptoms of delusional disorders, schizophrenia being the most well-known one. I think that you need a valuation by a psychiatrist immediately. The fact that you have recognized these abnormal thoughts and feelings so early on is important because it will allow you to get help before your situation gets out of control or before you make a mistake that has a lasting impact on your life. Good luck.