I need advice for my future.. careers, family, ect.. ?

OK, so I'm going into high school this year. I am quite smart. I am 2 years ahead in math, 1 year ahead in english, and 1 year ahead in science. I took a few high school cles in middle school. I would actually like to become a police officer, then a homicide detective, when I am older. Many people tell me I am too smart to be a police officer, and I should be something else that I can really use my brain for. I would actually really like to be an obstetrician more than a police officer/homicide detective. But an obstetrician must go to college for a very long time, and me and my family can not afford for me to go to college that long. I am going to go to college no matter what I do, I don't really have a choice. I also don't want to go to college very long because I really want to have children, but at a rather young age. I don't want to try to raise a child while I am in college, because I know it will be very difficult and expensive. But I want to start my family early, and not be having children when I'm in my 30's. Do you think I will be able to take college cles in high school and get a head start for college and be able to finish earlier? And I'm still not sure what I want to be, a police officer or obstetrician, or maybe something else. I'm really not sure.