I am glad that you took the time to write about your concerns. You have a sense that something is wrong and I think you may be correct.
You also described “watching from the sidelines” and on some occasions having conversations with imaginary people. Conversing with imaginary people may be a hallucination, which is a symptom associated with schizophrenia and other psychotic disorders. It might also be a manifestation of your extreme loneliness.
Without being able to interview you in person to gather details about your potential symptoms, it is difficult to know what may be wrong.
Someone told you that you have schizophrenia. Based on what you have described, depression may be a more realistic possibility.
It would be interesting to know who that “someone” was who believes you have schizophrenia. Is he or she a mental health professional? If not, then it may be best to devalue their opinion.
My two biggest concerns are your refusal to see a doctor and your belief that you cannot speak to your family about these issues. With regard to accessing help, you have eliminated the very people who are there to help you. These issues should not be ignored; they should be brought to the attention of a mental health professional. You are clearly suffering. You should not rule out the opportunity to receive help.
Even though you are reluctant to seek help, you should do so anyway. Are there school counselors or mental health professionals available to students on your campus? Most colleges have professional mental health services that are available to students free of charge. I would strongly advise that you utilize those services.
You stated that you have been trying to “figure out” what’s wrong but were unsuccessful. Mental health professionals are trained to deal with these types of issues. Use their expert guidance to assist you in dealing with psychological problems; that is their job. I hope that you will take my advice and seek professional help. Please take care.