Sadly, not all teachers are reliable, which despite being unacceptable when your exams are so close, you have to accept - otherwise your frustration will only hold you back (as experience has taught me). Watch Mygcsescience videos on YouTube, get a few CGP revision guides (good for all exam boards) and create flash cards/mind maps to help you revise. Although keeping motivated when you feel like you have no support is hard, just imagine Results Day in August - and getting a pleasing grade in Biology with absolutely no thanks to your teacher!
Good luck!