so...

Sorry, meant just "not happy to be a part of it," not "tomorrow"

Once you sign that bid card and accept a bid, you cannot rush again until formal recruitment next January. If you want to give it a little more time to decide, you can technically drop anytime before initiation and try again next year (regardless of if you do the pleading ceremony or not). If you go through initiation (probably 6 weeks from now), you can never rush an NPC sorority here or on any other campus.
As for your chances if you drop and try again next year, it's hard to say. Sometimes it works out and sometimes it doesn't. You'd need to think long and hard about what you're looking for and what would make next year different. Maybe confide in a trusted pledge sister, older member, bid day buddy or even your recruitment counselor? You may be surprised to hear that others have been in your shoes.
Also, don't let idiots on this website get you down. Despite what GR might have you believe, ALL chapters at BU are really great (not to mention strong on a national level!). Good luck!