Premed is not a major. It is an intention, it just means you’ll take the dozen or so classes required to apply to med school. People can do this with just about any possible major.
On a related note, why an M.D? When many HS kids become interested in a medical career it becomes “I’m pre-med!” and they embark on a path that will take 11+ years of school/training plus enormous debt. Doctors are far from the only ones in the medical field. It includes physical therapists, radiology techs, nurses, speech pathologists, physician assistants, nurse practitioners, to name but just a few as you can see on http://explorehealthcareers.org Unless you’ve carefully considered the alternatives and have spent time in a health care setting (which is an unwritten requirement to get into med school) its better to think of yourself as interested in exploring a career as a doctor rather than someone who has already made the decision.
As a HS student opportunities may be limited but you should try to get a job or volunteer position this summer and next school year in a medical setting (volunteer in a hospital, etc) to help you confirm that an M.D is the best fit for you.