I knew I wanted to do anesthesia in high school- keep an open mind but ignore the people who think you're crazy for knowing already. (I'd done summer research program that put me in the OR the whole time, and my HS had an affiliation with the local teaching hospital where a few of us did observerships half the day for our jr and sr years.)
I would caution you not to do the BS-MD programs, where you apply NOW to a 6 year combined college and medical school degree. Go to a 4 year college, work hard, and have fun. It will help keep your options open even if you're 100% sure you want to do medicine, plus I think the intellectual and emotional growth you undergo in those 4 years is invaluable. Good luck!