Hey! I believe since it's for a short period, that is, till the exam gets over, you won't have to worry about it. If you are feeling strenuous although you take regular breaks and exercise, it could possibly because of the mentality. You could be taking this so hard on yourself. May be thinking it as the only shot you have got. Such attitude can create pressure which will affect your preparation and hence your result. What I suggest is start practicing meditation and taking power naps. This will refresh your mind and make you peaceful and help you with your preparation in a better way. Don't worry this won't cause any physical damage. All the best for your exam.
I think when you are studying for something really big for that, it can be very tiring and you can get really anxious. Doing it over time helps make it less stressful. But none the less, it is a tedious process preparing for huge tests. But worth it! You'll be happy you spent this time as it will surely pay off. I agree to take breaks. Eat healthy snacks, avoid caffeine to stay away (there is a crash after caffeine), get rest when it is time, exercise every day, etc. I don't think it is damaging, just challenging. good luck
Hello~Short episodes such as you are experiencing by studying for an important exam, will not cause cancer, it is when a person in under continuous stress for many months and years. You are doing the right things by eating properly, exercise and taking small breaks. The headache is due to tension in your neck, once all the studying is over and you are relaxed, it will get better.
Good luck on your exam.