First of all, my best friend in the whole wide world told me that she thinks sororities are cults. I said, "Good, then don't join one...but what do you call those fraternities you love to party with so much?"
Second, my mother didn't want my to rush in the fall. She thought it was too soon, too hectic, and that I wouldn't know what I really wanted. Also, she and my older sister only had spring rush at their schools. At my school, formal rush was in the fall and it was A LOT harder to get a bid in the spring. Today, I am soooo happy that I didn't listen to my mother. To think - I would've missed out on a whole semester of my beloved Zeta!!
Either way, do what feels right to you. Just get involved somehow.
Lastly, do not worry about your looks. Any sorority that judges you on that is not worth joining. In my chapter, we have super skinny girls, curvy women (as I like to call them), girls who look like beauty queens, girls who wouldn't wear makeup if you paid them, knock-outs who date a new guy every week, and soft-spoken homebodies. Basically, any sorority worth anything will see past any physical appearance. Trust me, you'll find somewhere where you fit in. (Also, I am pretty sure that every sorority on my campus - there are 7 - have more than a few curvy women!!)