Severe Depression. Explain it everytime.

I am a 21 year old student currently preparing for civil services. I have always been a bright student but lately my problem of over thinking(EXTREMELY negative thoughts) and overstress has exacerbated to an extent where forget concentrating, I am not even able to form proper sentences while speaking/writing. This has reduced my confidence levels drastically because I was always a good performer at debates and writing competitions in my school days. My father is an alcoholic so I do not share a friendly relationship with him. We hardly talk. I have always been sort of an introvert but now it has become very hard for me to bear with this loneliness as the only person I had in my life hates me now. I think I'm slowly going into severe depression because now that I am not able to study properly, I feel like I will not achieve my goals and all my aspirations will merely remain dreams. I wish I could emphasize more on how tough this has become for me but I fail to explain it everytime.