Not being a professional in the field I would not diagnose you. I would rather leave that to a therapist or a pdoc. There is a depression test you can take on pc. I live with depression for about a year. What you have described I deal with at least 2 or 3 days a week. The loneliness probably comes from the fact that you may not feel comfortable discussing your feelings with people around you because they may not understand or they may judge you. Do not be embarrassed to see a therapist. Do not hesitate to seek help. What you are dealing with is not wrong. You are not weak. Sometimes it takes help to deal with a depression. Welcome to pc and best wishes.