I suffer from anxiety, but its not medically diagnosed because its not really everyday anxiety but in stressful situations like exams.
Im in year 13 and been fine with exams since, but recently ive become more anxious of my anxiety if that makes sense and its literally the fear on me getting scared in exams thats scaring me! Whilst im doing the exam all ill be thinking about is 'am I going to get a panic attack now.' So im not concentrating on the actual exam. Its all confusing I know.
PRO TIP. okay, this is seriously one of the best pieces of advice to help with my anxiety attacks that I've ever been given. it's a method often referred to as 'mindfulness', but basically it entails tensing up and then relaxing each muscle in your body working up from your feet. you tense for ten, release, and work up to the next body part. I now do this whenever I start to feel anxious or panicky and it seriously makes me feel so much better!!
It might be worth talking to your school just in case they can sort out a smaller room/rest breaks which might make things easier as it's just less of a big thing if the worst happens.
Practice relaxation techniques before the exam at home, if you know you can control your body and you feel confident using the techniques then you will be able to use them better in a stressful time and feel more assured that your anxiety wont ruin an exam.
You can try the technique above. Other things include deep breathing, put your hand on your diaphragm to feel the breath, breath in for 4 seconds and out for 4 seconds, grounding - list 5 things you can see, 4 things you can touch, 3 things you can hear, 2 things you can smell, 1 thing you can taste - basically try and bring your whole focus back to the present rather than being caught up in your mind.
Also sort out what you do directly before an exam so that you go in in the best mind set, get regular exercise, eat well, before an exam eat a good meal but something simple and then give yourself time for the food to settle so you don't feel sick, walk to your exam/get off the bus early, get there early enough that it's not stressful but not so early you have too much time to panic, don't talk to people who will wind you up.