I think as a junior, it can be easy to come off as a bit wishy-washy. You've survived on campus just fine without a sorority, so why now? Be prepared to give a thoughtful answer to this line of questioning. Share what you are hoping to achieve (and to give) by joining a sorority.
Keep your head up and stay positive. Take a close look at all of the houses. If anything puzzles you (and it might,) reach out to people on this board. After a few days of recruitment, there will be many (I hope) clear "yesses" and perhaps one or two "definitely nots." If you find a chapter that falls somewhere in the middle -- you're not sure about it, or you can't get a handle on it -- keep giving it a chance. It might be the perfect fit for you.
Yeah, some cuts will come your way because you're a junior. But you've made it in school, this far...you've got the right stuff!
Good luck, and enjoy your recruitment.