Help regarding test strategy!!

I'm a 12thie currently enrolled in PW RTS. I've found that I'm very bad at taking tests. I get serious burnouts and panic-attacks during tests to the extent that I've to stop writing and take rest. In the last mock test, I was unable to do anything for the last 30 mins and I froze...my hands were shaky, sweaty. I usually attempt P-->C--->M and this is costing my marks in maths. I'm able to solve quite tough questions at home but I'm failing badly inside the exam hall. I barely scored 25-30% in maths whenever I attempt it last. In P and C, I score fairly okayish.

Can you share your strategies that help to reduce panic-attacks during exams. Is it recommended to do Maths at first or after Physics? All are saying to do it at last but it is affecting it badly..Please help!!