Hello Stephiiee and welcome to the forums.
It sounds like you are really struggling at the moment and I was wondering have you been able to ask for help offline too? It is very important to do this.
I am a mum of two and being confided in by our children is vital. How can your family help you if they don't know? As a minor you need the help of your parents to get the support you need so this is step number one to take. Do you think you could try? Even showing them this post if the words are difficult.
It would help for your parents to take you to the doctor about this. There are medications that can help anxiety and also many techniques you can learn that dont require meds. Seeing your doctor is important.
If you feel unable to ask family how about a trusted teacher or school nurse or any other adult you feel comfortable speaking to? The kids helpline is a good place to try practicing talking about what you are feeling if you need a bit of help first.
Also... Is there anything happening at school which has triggered this fear? I know some parents will pack a spare uniform, underwear and wipes etc in a discrete bag at the bottom of the school bag just in case it is needed. Would having this help ease your anxiety?
I do hope you can return and keep talking when you feel able to.