Oh you have the exam anxiety ah.. no worry... small problem.
All you need to do will be these.
When you feel breathless follow the 2 steps below
repeat about 3~5 sets you will feel much better.
Me from sec to my Uni also got this anxiety problem.
Step1 Breath Deep in heart count 1.2.3.4.5 then
Step2 Breath out also count 1.2.3.4.5
Repeat the again..
Note. <Do not count too fast just normal or a bit slower even
better. >
This will make help you catch your breath and also help to
regular your breathing too. Plus when breath in deep more oxygen
will be circulated to your brain in another word it help you to
think better instead of go blank.