I don't think it's ever "too early" to start prepping for college. You don't necessarily have to start thinking about applications now. That being said it doesn't hurt, many applications ask for essays but you shouldn't have to worry about that until the summer before your senior year. In the meantime you can:
-Apply for scholarships
-Research universities you're interested in
-Take course at your local community college
-Prepare for tests (SAT, ACT, etc...)
-Consider teachers you'll ask for recommendation letters
-Plan college campus visits
At the end of the day you're still a junior in high school and you should enjoy that time with your friends. Don't stress yourself out too much.