I'd always say get advice and authorisation from a medical expert- not only because they will be able to watch over you to make sure the dosage is right and your getting the best treatment for your condition, but also because there may be side effects or reactions you may not notice and an expert might. Potentially it could save you unwittingly harming yourself or creating damage which can't be corrected. If your study is this important to you then surely it warrants getting professional medical advice rather than risking it all with self medicating?

I am assuming that you're in the US so not sure how the laws work over there, but I was sure that once you get to a certain age, your rights change and what is shared with your parents is up to you rather than done so by law as it is when you're a child. If you are worried about a medical person informing your parents, maybe ask them first where you stand on that because it may be you don't need to share anything you don't want to.