This has been covered many times before, but for the interest of procrastination, you have 2 options.
1. You enrol in melbourne doing science. You can then (after getting very good results) attempt to transfer into medicine. You would have to go to an interstate uni as no vic uni's offer transfers into med (in fact, monash is the only one that offers med to school leavers) Your enter is actually pretty decent (dont be hard on yourself) and your uni scores would need to be excellent. Actually, you would need a Distinction average (and high WAM) at the least to be considered for a transfer. Most importantly, make sure you cover ALL pre-reqs for med when you try to transfer. This means that if you didnt do chem or bio in high school (and i assume you need them for med) you will have to do them at uni and check with the uni's your applying for for what level of study in those areas you would need in order to get the pre-reqs.
As you can see, its a hard process and quite a bit of luck and work is required.
2. You do science (or any other degree, do what you will ENJOY. That is very important. If you dont think you will like science, then you'll find it harder to get good marks) and graduate. With a degree under your belt then you can try and get into a graduate entry med course. Melbourne uni has introduced the Doctor of Medicine which will be competitive, yet its entry is tailored for melb uni students (especially science and biomed, but dont let that make you choose to do those courses) If you choose to try for that, then you will have to take certain subjects at uni. Just google doctor of medicine melb uni for all the facts. There is also graduate med at monash (at gippsland) and graduate med at deakin (at geelong) Both are fantastic courses. Theres also the interstate option. For all options, you have to sit the GAMSAT (graduate med test).
Overall, i would choose the 2nd option. Graduate entry is a better pathway to medicine, you have more options and you can complete your degree without the constraints of the 'i dont even want to be here, i want to transfer' mentality (in my experience = better marks) Also, you can feel free to choose a degree for your first degree without constraints (melb uni is the only uni that has pre-req subjects for entry)
Some places to start searching for info are
medstudentsonline.com.au (focuses on school leavers, but lots of info. large community)
pagingdr forums (google it, more on graduate entry/those already studying a degree)
