In addition to what's been mentioned here (I'll second all of it, especially the music piano/keyboard thing - music's a great hobby to pick up)...
I highly recommend searching for a job. It wasn't until 18-ish when I really had to kick myself and start doing applications, so if I seem too hypocritical, you can wait until you're 18, too, but better earlier than later in this case.
I'm not going to lie, it's not easy to get a job, but having a source of income at all is very helpful in life. But it's not impossible; if you go through with the job search, do not tell yourself it is impossible. It's going to seem so, but keep going. I spent months doing applications, had up to seven interviews, and
eventually, found some fast-food kind of job. Not perfect, but having actual income is not a bad thing. Plus having some experience makes job-searching much easier later on.
Then there's other things about it. Your life won't seem as empty. I used to have trouble convincing myself I wasn't empty. Now I can't really convince myself I'm empty. Plus, it'll be difficult with social anxiety, but gradually, you'll get better. My first few days were crazy tough with the socializing, but it gets easier. Plus, if you're worried about how the co-workers will think of you as someone who seems social phobic, it doesn't really matter; as long as you can work with them well, they don't mind if you're a bit quiet and/or independent.
Just thought I might as well throw in my two cents.

I'm still looking for a real friendship myself, but like anything else, if you stop looking you're not going to find it. If you keep going, maybe you'll have a classmate next year who sits next to you, and perhaps you'll have the same interests. The year after, if you plan on doing college, there's clubs and organizations where you can find people with similar interests.
Just throwing a few things out there.