You can major in anything and still go to medical school, or train as a nurse or physician’s assistant. There is nothing wrong with being undecided. In fact it can be a plus if you are at a school where you can explore. Some universities do want you to have a major in mind, but at many or most you have until the end of sophomore year, and you can change even after that.
There are postbaccalaureate programs to cover the prerequisites for med school, if you don’t cover them during undergrad.
This need for certainty is understandable given the cost of college, and may be your family culture or personality. Both of which need to be respected… However, many enter college undecided and many change their majors and end up doing fine.
Certainly look into CS, which may or may not be what you expected. If you like math, you may like CS. But only if you like it.