Hi there, It's best to use credible websites (usually governmental, organisational websites) e.g. The Butterfly Foundation. Try to find some statistics to get you started (Make sure they're Australian, e.g. ABS), and maybe try the library/browse some magazines to get ideas for your project.
In addition to what laura-jayne has mentioned try looking at Media Psychology impacts on body image, articles on researchgate/ academia.edu, and mental health articles produced by the Department of Education and Training now Department of Education and Communities regarding poor body image and psychosis affecting wellbeing.