I think before your exams make either a teacher or exam invigilator aware that you're ill, HOWEVER, my friend in our AS english lit exam broke her leg and she needed doctor/hospital proof that she had and that way she got sympathy marks.
It sounds to me however, (I am no doctor of course) you kinda have a strong cold/flu. What I suggest is you keep hydrated and well rested, but of course continue to study but don't push yourself as hard, take breaks too.
I also enjoy to sweat my illness out so steam your face or even eat a curry.
Here is some advice quoted off the NHS - flu - treatment section.
Managing your symptoms at home, you can look after yourself at home by resting, keeping warm and drinking plenty of water to avoid dehydration.If you feel unwell and have a fever, you can take paracetamol or anti-inflammatory medicines such as ibuprofen to lower your temperature and relieve aches. Children under 16 shouldn't be given aspirin.
Good Luck with your exams, don't forget how important your health is over your exams. Health > Exams.