I don't think I can ever be successful in life. My stuttering is holding be back so badly.

I don't think I can ever be successful in life. My stuttering is holding be back so badly. I'm writing this because I'm just frustrated and depressed. I feel like my stuttering is getting worse, when I was a kid, it wasn't so bad, but now I'm 20 and it's just getting worse all the time. Sometimes I can barely string words together so I don't talk at all. I don't think I'll ever be able to have a girlfriend, or someday in the future get married and start a family. How can I when I can barely talk sometimes? I'm not particularly smart either, I'm just an average person, and I'm doing poorly in college right now (getting mostly C's and will have to retake a few classes I failed). Stuttering is also a big reason for this as well. I can't ask questions in class, I can't befriend my peers, I can barely speak to my professor one on one. Nowadays my social life is non-exist. I don't go to any parties, do any social activities, just school and I work part time. My friendship with my two close friends is drifting farther and farther apart (they've started dated and getting girlfriends). And as I said my stuttering is getting worse so I can't even talk with them. I currently live at home, and I have a fear I'll end up being a loser who just lives in his parents home for the rest of his life. Does anyone have any advice for me? Is there anyway I could increase my speech fluency? Or boost my self-esteem? I did speech therapy when I was younger, never helped and I don't have the time for it now anyways. Is there a book that could help me or something I could practice at home?