Medical career possible?

This might be a long question, but I need information on some careers that I have been thinking about. I am 16 and just recently got my GED. I am now in montgomery college. It's a communtity college. I want to have a career in the medical field. I wanted to be a registered nurse, but i wanted to go higher and be a nurse practitioner. What is their salary? I really wanted to be a doctor but not sure if that is a realistic goal because I got my GED and not my high school diploma. Is it a realisitic goal to become a doctor? I am committed to study as much as it takes but the whole medical school thing is it really as hard as everyone makes it out to be? That even if i study it will be hard to p? I really want to do this i just dont want to waste my time or money taking the cles if its more than likely that i wont succeed. Also, how does it work with paying it off? Do they give you awhile to pay off the loan. How long will becoming a doctor take me i wanted to be an obstetrician or pediatrician. How old will i be if im about to be 17 now? How old will i be when i finally pay this all off? I know this a lot of questions but i need a lot of answers to decide what im going to do with my life.