An encyclopedia will give you an overview of your disease or disorder and refer you to some basic articles on your disorder. These are all online. Check the bibliography at the end of the article.
A requirement of your paper is that you must use scholarly sources. But how do you know if what you've found is scholarly? Watch this helpful video (courtesy of the Peabody Library at Johns Hopkins University):
Use the following databases to collect scholarly primary research articles in the biological sciences.
Use websites to collect statistical data on your disease. Use the government websites below and websites from associations such as The American Heart Association and The American Diabetes Association. Remember to be careful what websites you are using.