With your interests in math, chemistry, and biology, you seem to be well suited to become a chemical engineer. Chemical Engineering is a very broad profession (e.g., bioengineering, environmental engineering, computer-aided design, new energy technologies, etc.) and has lots of interesting directions to pursue as you move forward through college. During the first couple of years in college, it is pretty easy to change majors as you find some courses that you like more than others and talk with students who are junior and seniors. I remember being insecure about studying chemical engineering in college, but once I got there I found that I could do the work if I wasnt afraid to ask questions when I didnt understand something. (I thought at first that people would think I was stupid then I learned that they just thought I was interested and curious.) And if you can get summer jobs or internships that are in areas you like, they will let you know a lot about the post-college professional options.
So best wishes, and know that most of us dont have detailed knowledge of where we are going just a knowledge of the direction of interest, the willingness to do some work, and the common sense to make good choices when new options appear. I have never regretted my choice of chemical engineering as a profession!