No offense, but if you were to jump into a career as you are now, you would not do so well. Before thinking about a career, you should consider self-improvement.
We are in sort of a similar situation, I think, but I'm two years older and currently trying to pull myself out of the ditch I dug myself into. I'm 30 and live with my parents, but I've been working at a grocery store for about 7 years. A few years ago I went back to school and now I have successfully obtained my Associate's and am currently at a university working towards my bachelors.
There are a lot of different things that can help you with your self-improvement success, but some are easier than others so let's start with the most basic: self-care.
This is the logical first step for several reasons: its the easiest task you can do to bolster the most rudimentary level of self-confidence without involving other people (helps with the social anxiety). I don't care what anyone says: you cannot do anything WELL if you do not have even a sliver of confidence in yourself. Are you overweight? Underweight? Does your skin look like shit? Is your diet shit? What you put into your body affects mood tremendously. Another reason why self-care is the logical first step is because simply working out and lifting heavy shit will release endorphins throughout your body. This is pivotal to your future success because it will instill in you the tremendous feeling of happiness. When I first started my improvement road map, I began with calisthenics at the park at night (didn't want to see people). I lost weight and gained some muscle over a few months and when I felt confident enough, I got my parents to get me a membership at my local gym. Yet another reason why exercise is the best first step is because other than giving you confidence, it will instill in you perseverance, dedication and consistency: three mandatory traits you need to succeed in NoFap. Working out will make you happier, you'll want to feel happier more often, you will go to the gym more often, you will be dedicated to the cause of working out to become happier, you will find yourself becoming consistent in your efforts, and you will persevere and break most of your anxiety to the point where you can feel decent in public.
That leads to the second step: starter job.
I know you mentioned you don't want a job, but having one, even a starter one, will aid in your self-improvement tremendously. In this stage, due to your efforts in your self-care regimen, getting and maintaining a job should be much easier. In this stage, focus on improving social skills (I suggest looking up videos from Improvement Pill and FarFromAverage about social skills) and just practice them on random people. Working in the service industry like a grocery store is great since part of your job is to simply greet people and ask if they need help finding anything. This is how I improved my strong eye-contact skills and small-talk skills. I'm not sure if you have trouble finding friends due to your social anxiety, but this is also a great place to start working on that skill, too. You will not be successful in a long-term job if you lack great social skills. It's that important.
The final step is school.
For me, this was the final step because it throws many different situations at you and will truly test whether or not you've exercised your basic skills. Group work, surrounded by people all ages (mostly late teens to early 20's). The anxiety will be crippling at this stage if you don't work on it before beginning this step. I had worked through my anxiety enough to attend class diligently, but I know that if I hadn't before I began school, I would not even show up, making going to school meaningless (and costly since it's college).
As for figuring out what you want to do, take a bunch of classes at a community college. I think there is also an aptitude test that can assist in finding your path. I discovered my passion simply by taking random classes.