I'd suggest you focus on what's important on a week to week basis. Keep a pad handy so you can write down what you think needs to get done. That way you don't think about it any more.
School is always a priority so find ways to possibly do homework before you leave school grounds so that it is done once you leave.
At work, focus on your job and use your lunch and break times to eat healthy and relax. Try to also take 5-10 minutes breaks throughout the day that will re-energize you.
Ask for help. There's always someone willing to help, so find ways to help others who can also help you.
It doesn't last forever....the stress you feel now from lack of time won't last forever. Just prioritize and do what is needed and leave other things for a later time, like Thanksgiving weekend or Winter break when school is out.