Turquoise Sea,
I wish you the best in sorting through all this. I also started out as a music major at a conservatory... after two years, I switched to a major in political science. I've never had a job that directly related to either one of those majors. Ended up pursuing master's degrees in completely different areas. I am not exactly the poster child for great career success right now... but I think it is pretty common to end up doing something different than what your college major is.
Lots of schools have career counselors that can help you to identify what you are interested in and what your strong points already are. That might be worth checking out.
This (college majors, career stuff) is a hard thing for most people to figure out when they aren't depressed... in my experience, trying to make decisions when I'm depressed is much harder. Be kind to yourself. And, just because you made a choice as a teenager (majoring in music) that you might do differently now does not mean that you are an "idiot" as you put it... you are probably just in a different place in your life now than you were then.
Take care,
garden gal