I wasn't sure what I wanted to study in college until several years into my higher education (when I was around 22). I went to college guidance counselors, talked to other students, and did research on careers, but still I had a hard time narrowing my course of study (I had many interests). Initially, this wavering was very expensive (because I was attending a state university), but when I switched to a community college, I was able to experiment with different career paths at a significantly lower cost. Eventually, I figured out the academic path I wanted to pursue, and made my way back to a state university (achieving my B.A.).
I suggest that if you're not sure yet what you want to study, take courses at your local community college, try adult education classes on particular topics, explore some workshops or online courses, and/or talk to career counselors and students enrolled in programs that interest you. Gather as much information as you can, and test out courses of study at lower costs.
Below are some resources on Education.com you may find helpful as you explore your college options. All the best to you as you pursue your academic goals!