Most of higher secondary students feel worried in exam time !
here some tips to get stressed out :
First of all, you need to relax , then identify the reason of stress.
if it is your nature to get stressed out easily then try yoga! If your anxiety becomes acute, then you should see a doctor.
if you not prepared well for exams then i think you are the safest, because it is very natural for all to get worried about your exams! that time you may try to do anything other fun things, which will make you happy and worried free.
if you totally not prepared for your exam at all then i think you still having time for study,if you can manage well. The fact that you have left it to the last minute indicates that you have done this before and are confident you will do it this time too.