This is a difficult situation.
In your position, I would defer for a year, and shadow a teacher or something like that. No profession is perfect. Being a teacher involves dealing with a lot of behavioral problems, taking on extra work during vacations, babysitting, and sometimes working in dangerous environments (though being a doctor is surely the same in this regard). Being a teacher doesn't have perfect job security, but Australia has a shortage of good science teachers.
If you stay in medicine, there are ways to ultimately end up at a similar position. You could go into lecturing, you could still go into high school education, you could go into policy if that interests you. Both are people oriented professions. Keep that in mind as a comfort for whatever path you choose - your life course will change a lot over the next 50 years.
Furthermore, most professions involve you being a slave for something for a while. I'm strongly considering entering academia, but that requires 5 years of PhD + 2-6 years of being a postdoc, where you work in someone else's lab with quite modest salaries... and with no guarantee of ever landing a permanent position. I'm torn because I know I could enter something lucrative like investment banking and rake in the cash, but I'm passionate about physics.
Sorry to play the devil's advocate, but think through the pros and cons of this situation. I know a lot of people who've been in your shoes, and I had a friend who wanted to transfer out of medicine, but his grades were too bad because he hated it so much. He described himself as being trapped for life. I'm sure you'll make the right decision for you, and I'm sure that irrespective of what you choose, you'll find a niche that suits your interests and personality.
Edit: If you do decide to transfer, will your parents definitely throw you out? If so, do you have the financial resources to support yourself? That's a big thing...