Aww Nichole...
I'm sorry!
So, if you do wait until next fall, what will your class standing be? Because I am worried that you may then have the age thing held against you? I'm not sure about MTSU's general feeling on "older" girls getting bids, but seeing as it seems hard for many "southern competitive" schools...I know you loved XO, and the other group that cut you, but you DO still have groups left. Look at amandamarie! She was so disappointed but went to Alpha Phi pref and loved it! She even said she felt like she was getting a second chance to see how great the house was (and she had already had 2 parties there!). And sugar and spice, who has proven to be a die hard DDD, told us how last year DDD wasn't in her top three for a long time! Maybe you should just keep going through rush and see if someone else sticks out to you. I know that might mean Chi O misses out on a wonderful PNM, but it means another house might just get her! I really think you should keep going. Nothing says you have to pledge...
Good luck!