You remind me of me. My anxiety destroyed my self confidence when I first got into college and I still wish I could go back and fix it. But there are some things to keep in mind, I think.

You not being prepared for this exam will pass. Despite how you feel right now, and I am not at all trying to belittle you because I have done the same thing and probably will again, this exam will not determine your self worth nor will it decide how you will do in the future. I used to blow up exams into these end of the world size things. And I would vomit from the idea of needing to sit down and actually take it because I was convinced I was going to fail, therefore I was going to let everyone down. So even before I took the exam, I created a future for myself and I was convinced that future was truth. It never was.

Do not worry about your friends. Worry about yourself. It isn't cruel to do so, especially when it comes to school, work, etc. It's a practice of self preservation. And it's hard to get into, but it takes practice and consistency. Tell your self that you're the important one right now and that you're doing your best, even though some of your mind is telling you otherwise.

It's a lot to overcome and it might not get easier in a few days or a week but you will get there! I still have my moments whilst I sit doing homework that I am convinced all I am good at is failing and making a joke of myself, but I have to bring myself out of that thought because I know I will get trapped if I don't. It's the curse of being an anxious perfectionist.

If anything, for this exam, I'd say get into contact with your professors. Explain the situation, say you can provide notes. And ask for a bit of an extension. The worst thing that can happen is they say no. It's always worth a try.

Take care!