Hi,
Congratulations in completing your 12th. It is good that you have made up your mind to do research in the field of medical science. Although the best way is to go through MBBS, since you are not interested in it, you can try a Bachelors in biosciences (biotechnology, mircobiology, biochemistry etc.). As such, for doing research in medical sciences, you can even go with an MSc in Chemistry or Physics also. There are physicists developing new technologies in applying spectroscopic techniques in medical sciences. Some of them are applying techniques in physics for studying activities of stem cells. All it matters is how you select your research problem. I would suggest you to check websites of some international universities and go to their medical science department website (eg. www.muh.org.au). You may get better ideas while you check the profiles of faculty members and researchers in such departments.
All the best.