It sounds like you are asking about career options with various college degrees. The options are pretty much limitless. For example, just doing a quick google search for careers with an english degree reveals this page which includes a long list of career options for people with english degrees. You can see how many different things can be done with an English degree. The options are similar if you look at almost any other field. I think it probably makes more sense to start with what things are of interest to you and then narrow things down from there. The good news for you is that you don't need to select a major for a few years.

If you are considering medical school, you can start out taking the required pre-med courses and any other college requirements. You can use your elective time to take courses of interest to you. You should discuss your interests with your advisor at college to get ideas for coursework that would best suit your interests and may also help you decide what you would want to do for a career if the medical school route doesn't pan out. I think the important thing to discuss with your college advisor is to select the courses that will give you the most options until you have a better idea of what you want to do. If you are passionate about music performance and you have the skills to pursue a career in that field, you should give yourself a chance to follow your passion. You don't want to always ask "what if" later in life. I have always believed that when it comes to education and career choices, keeping your options open is the best choice whenever possible.

As for becoming a teacher, there are different requirements whether you want to teacher kids or college level students. I know that you can study to be an elementary school teacher and get a bachelors degree and meet any state licensing requirements, or many people go back to get a Masters in Education after obtaining a bachelors degree in a field other than teaching. The Masters in Education programs are designed to meet the state licensing requirements. For college leve teaching, I don't think there are state licensing requirements, but you would have your best chance of getting a job if you have either an advanced degree or significant experience in a particular field (which obviously you wouldn't have coming right out of college).

Search the interests and desires that lie in your heart. sounds cheesy, but do it. Pursue those interests, not prospects. If you are not 100% sure about what you want to do, for example becoming a doctor, then spend time after high school in that vocation. Become an EMT or get an entry level job at a hospital or clinic and work your way into shadowing a physician. Only then will you truly learn if it really is for you, and taking this route, although more lengthy than jumping straight into college after HS graduation, is a much more surefire way to find what you want in life.

I didn't know anything about medicine but had an interest, so I joined the military as a combat medic. I got to work first hand with physicians and physician's assistants as well as other primary care providers. I got to act as a primary care provider in many situations to many Marines and some civilians. The experience revealed my interest in the medical community as a primary health care provider, and put me through tough situations to test whether or not it is something I enjoy as much as I thought and said I did.

I am not advocating that you join the military (although because of the time I served I now attend a private university in southern CA for free), but that you take time to explore some options in real world scenarios. Society is a very big place that you will not know of until you plunge in. People who jump straight into the commitment of college studies, graduate studies, etc, without any hands on experience or OJT in their field of interest run a huge risk of backing out of that commitment or losing that interest when they find out what it is really like to do that job in the real world. Many people don't even make it past the studies and drop their majors altogether, leaving them at the crossroads once again.

Go out there and get your hands dirty in what you want to do! College is great, but experience will reveal your true interests without student loans.

I wish to you the best of luck.