It is ok to have doubts. You don't have to be sure about what you want to do with your life. There are very few 18 year olds qualified to choose the correct path for their future self.
The trick at your age is to preserve your choices. Don't limit your options in the first two years of college. As most people would say, get a degree in anything but aviation. Also don't spend more than is necessary to get your certs and ratings. The University may not be the prudent financial choice.
Why do you want to be passionate about aviation? Is it that you want to be passionate about something and aviation seems as good as anything else?