double.diamond - you seem confused about the "mechanics" of becoming a physician; perhaps I can help you out.
1.) Medical school is not twelve years long. To be accepted into medical school most people have completed an undergraduate degree program (BS, BA) at the very least. There were many people in my medical school class with advanced degrees (MS, MA, PhD) also. There were a few students who had graduated from college in less than four years, or had not graduated, but had completed the minimum requirements for admission. The next step is medical school. The curriculum at most US medical schools is four years long. There are a few combined BS/MD programs that are six or seven years long, but these are rare. After medical school comes residency which lasts anywhere from three (internal medicine, pediatrics) to seven years (Neurosurgery). So, depending on your choice of specialty, plan on the entire process taking eleven to fourteen years after high school.
2.) As has been suggested above, go to the best college you can get into, and afford to attend. Admissions committees prefer students who challenge themselves. I had a friend in medical school who went to a non-competitive college so that he could get all A's. He struggled mightily with the competition in medical school.
3.) Major in a science in college. I went to medical school in the early 1980's during which time there was a thrust to diversify medical school classes; there were a lot more humanities majors being admitted. My impression was that, as a rule, they struggled with science-heavy curriculum of medical school. Chemistry and physics majors do well, engineers also. Biology majors are a dime-a-dozen.
4.) Do well on the MCATs. There's a lot of standardized testing in medical school and residency and the admissions people want to know that you can make it through this. Show them that you can.
5.) Go into medicine becasue you enjoy it, not to make a lot of money, because you won't. The doctors of my generation and earlier generations made lots of money, but every year we seem to make less. I think it's safe to say that in ten to fifteen years we will have some sort national health plan. So it goes without saying do not, I repeat, do not incur substantial debt during the process because you will struggle to repay it.