Hi,
I don't suggest any tablet or therapy for this problem. This anxiety before exam is common for every one. But if it's beyond your control, that your sleep is utterly disturbed then only go psychologist to train you in that aspect.
Please read a book or pray if you are habituated to do or do breathing exercises before you sleep. Also take a glass of milk with honey which is a small home remedy to get sleep.
Health Tips
Read my article on FB on sleep deprivation
https://www.facebook.com/103122402375788/posts/pfbid05qT3yuUcpe4HKTfKMT5GCBAzWBcjE7En93tFnFcNwTjJpzLoKiagbwrRT53PoWupl/?app=fbl