Ok here's an extremely helpful chunk of advice you can remember: Think about whether or not the things in your life that cause you stress can be controlled or can't. If they can, do what you have to to change them. If they can't, and these problems are external, (impressions of other people, worrying about other people's problems) forget about them.
All you have to do is focus on the things you can change. If your mother is worried, don't let her stress become yours (and don't let her dump it on you, either).
What you seem to be doing is making your job issue affect you at school and other aspects of your life. When you're at school, focus on school, then afterwards find time to work things out with finding a job.
Make a list of things that stress you out and get it all organized so you know what you can tackle next. From what you've written here, the only problem you have is with finding a job, so keep working at it.
Life isn't always easy, and you're not alone. We all have tough times. You'll get through this, and it'll make you stronger.