I think your original question may be the answer. Your boyfriend’s behavior suggests depression. He is withdrawing from things he used to find satisfying. He is isolating himself. He is very self-involved and doesn’t seem to think he has the power or strength to change the way things are going.
If your college has a mental health center or an advising department, I suggest you talk to him about seeking some help. Many, many young people start to question whether they are in the right school or studying the right thing while they are in college. Many, many young people go through a period of confusion and even despair as they try to figure out what to do with their lives. Some conversations with either a therapist or with a school advisor might help him get back on track.
All you can do is be there for him. You can let him know that you are concerned and that you think he has the strength deep inside to face his problems and get some help. You can offer to go with him to his first appointment if he likes. If you are worried he might hurt himself, you could share your concern with his family so they can take a more active role in helping him. Ultimately, though, he is the one who has to accept that he can’t solve his problems on his own and that it is okay to look for some guidance and support.
I’m so very sorry that he is having such a hard time. Worrying about him must be taking a toll on you. If he refuses to accept any help, I suggest you seek some advice yourself. Taking responsibility for your boyfriend is too big of a task to do on your own.
I wish you well.