I'm loving my life and living my dream job. I work in IT and wouldn't change for anything except to maybe teach IT. Personally I love computers.
At your age the two smartest things you can do is:
1. Get excellent grades. Med School is tough to get in to. Get good grades
2. Make sure you surround yourself with as many positive people as possible
If you're around a lot of partying junkie type friends. Loose them. You need to be around other positive college/university bound friends. They'll help keep you focused.
Find ways to get an early foothold in your career. Talk to Doctors, volunteer, talk to people, network, anything. People will start to notice you. After a time, opportunities will start to present themselves. Grab them and don't be afraid of change.
Follow those simple tips and in no time you'll have your goals.
Last but not least, never give up. If you can't attack something head on, attack it from the side. Chip away at it. Just never give up. Visualize success.