I don't know if all of this is going to apply to you, but it's just some general lines of advice that I know have personally helped me when it's come to a situation like this. So hopefully it'll help you too.
Know that it's not your fault, and that you shouldn't need to feel guilty for things going on between your parents. Don't feel like you can't say how you feel about things either, because although it might be more difficult between your parents, that doesn't make things less difficult for you. Separate yourself from the situation if you have to. Get your own study room, focus on the immediate situation that it's 2015 and this is your HSC year. Divorces often take a while to mend; as a result recognise that you might not be okay with it quickly, and that's alright, even if you have to rely on time to heal it. So control what you can control. Do with what you have. You can still do well.
