Just talk to your maths teacher, and maybe head of curriculum about what happened. Remember, hsc is not the end of the world. Just work on calming your nerves, and if it gets serious over time, maybe go to a GP/counsellor?
fuck imagine losing 11 marks in an internal maths exam, why even bother with life anymore might as well head over to the cross now and become a prostitute because thats all you'll ever amount to anyway after losing those 11 marks