Hey Sam, I'm sorry you feel terrified about going back tomorrow. I figured you would and that's totally understandable considering how you've been feeling and that you've been away on break for a while and not doing well during that time.
There's probably nothing I can say to make it any easier for you, but do try to remember though that you have a plan of sorts in place and you can go to the school nurse if it all becomes too overwhelming. If you can keep busy today/tonight as much as possible so that you're not overthinking about tomorrow then that may help a little.
You're not alone in facing tomorrow. It's not a brick wall even though it might feel that way now. It's actually a flexible environment you are going back to and the school is there to help you.
You have your family and the school personnel who are aware of what has been happening for you. It may be really helpful if you could contact one or more of your friends and maybe travel to school with them. All those people are all there to support you in this transition back to school. Even though you don't feel that way now, you can get through this tomorrow.
It will be busy and it will be noisy. All of those things you fear. However, if you find yourself feeling overwhelmed then you go to the nurse's office as planned.
What concerns me the most is that I get the feeling that you seem to think of yourself as facing this alone and you really are not
alone Sam. This is not something you have to do alone. You have the support behind you and that can get you through. You may find it really difficult, but you can do it despite that.
thinking of you