It's not unusual to have a hard time finding a job you're happy in with so many people getting degrees, and the competition for jobs getting worse. I think young people have it particularly hard because they've been promised so much out of their degrees - there was definitely a culture at my school of just pushing people towards university, telling them that it would be worth it in terms of life chances/grad jobs, even if it wasn't right for them. Which leaves many young people leaving university often being unable to find any job, let alone one they want to work in, after having been promised so much more. Just out of interest, can I ask what type of work you have done, and why you left/got fired?
Have you thought about doing internships? I've just graduated, and on my second graduate internship (did a v. short one in summer of 2nd year), and have been finding it really useful to work out what I want to do and what I value in a job, whilst building skills at the same time. And whilst it's entirely your choice, I would also recommend not writing off jobs that quickly (you mentioned you've left previous jobs only after a couple of months) - people can make career changes at any time in their life, you don't need to know what you want to do right now, and you can always apply for different jobs whilst in a current job. At least it would help with feelings of isolation etc. And I know a few people who just went into any job, worked their way up to manager or similar, then applied for a job in a sector they really wanted to work in - with the manager experience, it was easier to get in, particularly at a more satisfactory level.