The fact of the matter is the jobs you claim you are interested in are all super hot types where plenty of people with better academics and without the handicap of wasting years in the medical school are desperate to get in as well.

I seriously doubt abandoning your medical studies now to take up an economics degree from scratch will get you anywhere near those jobs you seek. Maybe a Finance related department in a MNC or BO / research based roles in banks possible, but anything more forward then that is a shot in the dark.

I get a sense in your post you actually don't know much about Finance beyond a general idea that it is sexy to be fund manager. The jobs you listed like IB, hedge funds, private equity are quite different from each other. Why not you describe more in detail what you think each of these jobs are and what you think you will be doing on a daily basis in each job?