I suffer the same problems with you Happy, I can never ever sleep and some nights I stay awake all night for all my life. Well for me, this is because i think too much of what's ahead of me. I'm always thinking and it just never stops. What I normally do is get a telescope and observe the stars all night. But since this has only been happening after your legal exam, your irregular sleep patterns can also be related to depression. Even though the exams are over and you don't feel stressed at all, short-term insomnia could be typically caused by such things as stressful episodes(maybe being really anxious for the year 12 exams) and the stress which has been built during the exam time can have a significant affect on you now. But right now, I think the best medicine is your inner-self. Whether it is your performance in your exams or something to do with your personal life, you need to let go of these things and free your mind or otherwise the issue you have will become permanant.