The good news is that you're only 20. That leaves the majority of your life ahead of you.
Lets first address your issues of madness and loneliness in a tiny room. I've been there as well, it really is horribly painful. The trick, is to learn to think about other things. It won't be easy, and I'll never tell you it is. But it is possible. I presume as you are posting online, that you have access to a computer. This is a great starting point. A computer can open you up to a world of people, and opportunities, shopping, and other resource gathering.
Best of all, computers can help you improve your knowledge. Knowledge is key, it can lead you to small victories. Small victories are the key to improving, they build confidence. My small victories led me to some great things in the long term, and they can for you too.
I practised two things I was interested in. Computer science in various fields, and fiction novel writing. Eventually these skills got me an online job part time doing technical support for a community of game makers learning programming. I got that job by participating in that companies online forums, they posted a job and I had developed the skills needed for it. I provided youtube videos to other developers helping them code. Eventually I then wrote a programming book, which an American guy discovered and now I'm producing online courses and teaching people computer programming world wide.
Why am I telling you this? Because big things come from many small efforts. If it wasn't for those hours studying the subject in my own way, I couldn't be doing what I am now, the same can happen for you. You have one important asset, time. Pick something that you enjoy, that takes your mind off your life. Enjoy doing it, let it expand you into different things. If you get bored, learn something else, do something else. Keep improving yourself, and you'll find the confidence to overcome your other issues.