It is entirely normal for a high school student to not know what they want to do with their careers. For those high school students who do know, it is very, very common for them to change their mind. One daughter I think when she was a junior in high school came to me and was concerned that she did not know what she wanted to do for a career, whereas her friends did know. I pointed out that yes her friends did know what they want to do, but in six months they will have a different plan, and in the end they will probably settle on yet another different career path. This is normal.
There is quite a few careers that are possible with a degree in mathematics. It turns out that a lot of what we take for granted in our day to day life only works because someone did the math. As a math major, the other students who I knew who graduated with a bachelor’s degree in math ended up in a wide range of careers. One or two went to law school. One got a master’s degree in acoustics. It turns out that there is a lot of math required to design a concert hall where every seat has good sound quality. One got a first job working at a cyclotron helping to do the math required to keep the beam of high speed protons focused and aligned. Some got various software engineering jobs, in most cases jobs where there was a lot of math needed to solve problems and the amount of data was large enough that computers were needed to do the computations (but a human needed to make sure that the math was right). A few went into artificial intelligence or machine learning (although this tends to be more recent, mostly). Some math majors go into accounting or quantitative stock investing. There are lots and lots of possibilities, and as a high school student you are not going to be aware of most of them. At the point that I graduated university with a bachelor’s degree in mathematics I still had no idea what I would end up doing, and then I ended up in a field that did not even exist when I graduated university (but that needed math).
Similarly there are lots of options in the various sciences. You can get to university, take some science classes in several different areas, and figure out what you like best, take a bit more of that, and see how it goes. Generally we each figure this out over time.
In terms of medical school, this is a path that requires a huge commitment of time and effort and hard work and college funds over an extended period of time. The people I know who succeeded on this path were very strongly driven to do it. If you are not strongly drawn to it there are lots and lots of other options.