I'm sorry to hear what you're going through. It's difficult and upsetting when you feel hopeless about your situation and moreover have no social support to make you feel better.
Having a minimum wage job in itself does not equate to being a "complete failure". Think of it as part of your journey towards achieving what you want. Do you know what your ideal job is (the industry, the skills required etc.)? Would it be possible to get into that line of work slowly, perhaps by volunteering in a related field, or in a role that will allow you to acquire these skills? Is it possible to take up short courses in that field, if finance is a concern for another degree?
There is definitely hope for you, even if you're finding it hard to see at this point in time. Take steps towards achieving what you want will allow you to see that light at the end of the tunnel.
And one more thing - life is not a linear journey. You'll take detours, you'll go in circles sometimes. You'll learn something new with each experience (even an unpleasant job can teach you what you don't like about a job, which means you'll know what to avoid in the future). I know it's difficult, but it's important to pull yourself out of the cycle of negative thinking when things get tough and take steps (however tiny) towards creating the future you want to have.