What kind of programs or miscellaneous activites can i do over the summer to get a headstart on being a doctor?

I'm 16 years old and just finished my sophomore year in high-school. Although I feel I have a natural talent in my math and science classes when I apply myself, I slacked off during most the year. Recently I have asked myself where I want my life to go and a recent epiphany that I had in my bio class that lead me to becoming a doctor. After thinking for a while I came to the realization that that would be a perfect career field for me. I want to get started right away so I was wondering what kind of programs and classes over the summer should I get myself into. I come from a medical background so the possibility that I could intern and look over one of my uncles could help me. Classes and programs to I just need some advice on what to get myself involved in so that I may touch the surface upon the career path I have chosen. Anything helps thanks