Relax, and take a deep breath! While some people seem to know from the age of 10 that they are destined to be doctors, most people really have no idea, and, even if they say they do, ten years after graduating college you will find them in a career unrelated to their degree! How are you supposed to know what you want to do if you haven't tried it?
Good news! There are free college classes on-line. They are called MOOCs. If you want something a little less intense, try the ed2go.com website. These are classes that run for 6 weeks, with 2 lessons a week. They are usually about $100 each.
There are several factors that are important in helping you through this process. Are you living at home, and, can you keep living at home after school, or, do you want or need to become independent? Will your parents pay for schooling, or, are you paying for it?
Sometimes it is easier to figure out what you do not want, and start narrowing it down that way:
Science( research, veterinary, climate change) /Medical/ Healthcare support (radiology, physical therapy, admitting office, dietary technician)
paralegal/attorney/document retrieval specialist?
More good news: Many people change jobs every 2-5 years. No longer do people stay with one company for forever. So, you can start out in one field, and cross into something else. To do that, you will highlight your "transferable skills" on your resume. So, if you start out working for a mining company, you could later get a job at a bank specializing in lending money to mining companies. And from banking, can go into financial planning, etc etc. etc.
It's really not necessary to nail it down right now! BUT, the important thing is that you don't go out there and just start drifting through life. Before you know it, you will be 40, wondering where the time went. So, a general plan is important, even if you don't have specific goals. If it is affordable, I'd recommend at least a 2 yr degree in some general field - marketing, business, etc. OR, consider military service, Peace Corps, or something like that.
Hope this has been helpful!