Lucy,
How do you currently feel about your pregnancy? I know that it's been traumatic and just know that everyone - everyone makes mistakes... Have you considered the financial side of things; how will you support your child? I hope you've got the backing of your family. They mean the world in these types of situations.
There are some pathways to finishing your HSC, and taking on that AND a pregnancy would be a lot to handle. Have you considered leaving school for a year and then completing it the next? Maybe split your HSC over two years as some on this forum have done.
I don't want to force down my opinion on you. Ultimately, the decision to abort the child is going to be your decision. The best thing to do is to be informed about the choice you will make; should you abort the child, perhaps consider the fact that you may regret it later on... should you not, how will you care for her? Did you have other plans, like going to uni, that may be interrupted?
If you need a hand just PM me!