Please help i have a concert in 4 days!?

I have a concert in my school in a couple of days. I sort of have social phobia and im having hypertension right now! Im super scared!!! I really dont want to do it but i have too. Everytime i simply play for me teacher my hands shake. I play cello and i like it but when i play infront of someone or people my hands get super shaky!! Please can some one help!!? I just feel like dying rightnow..