Have an Answer?
College is your time to experiment with different careers. If you're interested in Advertising you should talk to the professors in that department and ask them more about the industry. The things that make it exciting and what challenges you might face in the field. If you have the time, you should do an intership. This will give you first hand experience and will help you decide if it's the right path for you.
You won't know until you try it and learn from the people who've been there. Try not to stress out too much. You have more time than you think to change your mind about what you want to do with your life.