I think having restarted year 12 twice now (so you have repeated it twice, for a total of three attempts at year 12?) may realistically rule out most medical schools anyway.
Have you done any work experience for either medicine or radiography specifically (as opposed to more general caring work experience common to any healthcare professional degree)? This might also help guide you on what the work is like. Remember the degree itself is a means to an end. You'd be applying to medicine to become a doctor and have a career as a doctor, not to do a medical degree - that's just the necessary middle step. I don't think its uncommon for doctors to have been dissatisfied with their medical school experience but still enjoy working in clinical medicine once they are qualified.
However as noted I think even if you decide medicine is for you, you will need to try and find medical schools that would accept you in your situation as many either may not accept those who have resat (including sometimes restarting year 12) or may consider them less competitive.
It's probably sensible also to think about why you had to go through year 12 now three times and if the reasons are going to be issues during a medical degree (e.g. if you struggle with exam taking, regardless of your knowledge of the material, that may be an issue in a degree which has a lot of exams like medicine as I understand).