Do you feel like you have purpose in life? Sometimes a sense of purpose through service to others helps reignite interest in life . . . But that's just one way.

I guess you don't feel like talking in public. I see myself force to ask you questions but you are free to pm me if you don't want to answer them in public.
I was living for 7 years of my life like you isolated in my own world. It's fine to have a rich mind and being interested in learning. But, social life is also needed bc it's in our nature.
I guess you lived a bad experienced that was the last drop.
Ask for help. I deny myself to ask for help bc I didn't want to bother anyone. If you feel sad or lost nterest in things you found before as exciting. It's a warning sign that sonething is not working properly.

Try new subjects, perhaps.

Why are you at home 24/7 , is that a choice or a necessity? If it's the former , you should get out and discover the big wide world while you can. You've only got one life , don't waste it away behind the same four walls, you're young , seize the day.

I do get lonely sometimes and I do feel sad sometimes but the causes for sadness I can't explain. I just feel like I don't care about anything anymore.

I don't really know because I've never taken the time to notice. Btw thanks

Yep. Get out and move around. Find a like minded community. . . I need to do these things as well.

My mom said she thinks it's because I don't get out or have any friends coming to visit me. Could this be it?

Do you feel a bit depressive? Or have any confident problem? Or do you enjoying being alone?

Perhaps, you will be into this in another moment. If you are having other problems, perhaps you feel a little apathetic. You are the only one who can give an answer to your question.
Be awared of your patterns in your life. I mean, do you lose interest in topics frequenly or very fast...btw; nice interests you have.

Twister hit the nail on the head.