In any profession, you have people who hate their jobs and those that love it. It is impossible to say which career will bring the most satisfaction to YOU. It really depends on your personality, your goals, and your lifestyle preferences.
I would recommend that you start by going to a guidance counselor who can offer you basic career and personality testing. You should make sure that you job shadow or volunteer in a healthcare setting. However, don't limit yourself to considering only medicine or nursing. There are lots of other professions in which you can "help people", within the healthcare field and even outside it.
Your situation reminds me of my own career indecision when I was in high school. I graduated as valedictorian of my high school class. I always thought that I would pursue medicine, until I started thinking about goals that I had outside of my career plans. I finally decided to go with nursing because it would allow me to have a family and be an active participant in raising a family. That is not to say that physicians don't or can't have families, but it just wasn't the lifestyle that I wanted to have. I also discovered options, like becoming a nurse practitioner, that would allow me to have a lot of autonomy in my career. In general, I felt that nursing provided a lot more flexibility than medicine would.
Fast-forward several years and I am at peace with my career decision. I still don't know if I would have chosen nursing if I could do it all over again, but I am so thankful that I didn't chose medicine. I discovered early on that I don't enjoy clinical nursing. Luckily, in nursing, there are a lot of non-clinical options. I suspect if I would have went into medicine, I would be one miserable physician, because there just isn't the same flexibility to change specialities or find work outside of direct patient care. I am currently working on a master's degree, which I am using as a stepping stone to a PhD program in a field outside of nursing, but still within the healthcare realm. I don't know if I will ever directly use my nursing background, but I know that it will always be an asset. So, I will not say that I regret going into nursing because education is never wasted and I have learned so much about myself and life in general from being a nurse.
You can learn more about the pros and cons of nursing by browsing this site. The pros for me include the flexibility and the educational opportunities. Also, it is relatively easy to find a job, which is a plus in this current economy. The cons of acute care nursing for me were the long hours (12+ hour shifts sometimes with few or no breaks), having to work nights, weekends, holdiays, and rotating shifts, horizontal violence (bullying, harassment by coworkers), high nurse to patient ratios, and other unsafe working conditions that led to high stress levels. But again, it really depends on the person and the type of work that they prefer. Also, there are nursing opportunities outside of the hospital, although you should understand that it will take at least 1-2 years of hospital experience to be considered for these positions. Good luck!