Hi there!
Unfortunately this would not be possible at Monash, as starting tertiary study will mean you are no longer considered a school-leaver. Below is an excerpt from their domestic requirements.
Our Direct Entry Bachelor of Medical Science and Doctor of Medicine (MD) offered at Clayton Campus, is only available to applicants who have completed Year 12 studies (or VCE equivalent) no more than two years prior, and have not commenced other studies at a tertiary level during that time. Applicants who have commenced tertiary study, including AQF Level Certificate IV and above, are ineligible to apply for this course and should consider the graduate entry program.
However since UniMelb undergraduate degrees aren't eligible for Monash graduate medicine, if you continue there you'd be ineligible for that pathway. If you wish to try for Monash, you'd need to transfer to one of their degrees and complete a minimum of 96 credit points. You can find further information on their FAQs
here.
Best of luck!