Marie:
This is a normal part of parenting. Unfortunately, I think you are worrying about the things you cannot control and the minutia. I would talk to a doctor about getting on some anxiety meds or a therapist to help you compartmentalize your anxiety.
If you use the internet to diagnose yourself, you are only going to make yourself CRAZY!!! Stop thinking you are sick or have something and do NOT use the internet to try and find out what you THINK you have.
The only way to relax and stop is to learn how to compartmentalize your feelings, rationalize what you are feeling and stop freaking over things you cannot control - you cannot control when your parents die...you cannot control things that happen in school...please seek a counselor to help you get your feelings in order
GOOD LUCK!!