This is a very stressful time in life - you are getting close to graduation, and ideally, complete independence. In addition to worrying about your grades, you also have to start worrying about how you will support yourself. I think that these are very good reasons to be stressed out.
How many classes are you taking? You need to make time to squeeze in some physical activity every single day, for at least a half hour, preferably outdoors in the sunshine. It will make you feel much better emotionally, and will make your burden seem easier to bear.
You should also look into participating in some school activities so you can connect with larger numbers of people if you don't feel you have the time to devote to a part time job.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?