First of all i think you should try Heather Diet's and start using a soluble fiber supplement (if you don't use the one sold here I would suggest benefiber). It's really helped my IBS D. Getting control of your symptoms will really reduce your anxiety. Also try the hypnotherapy CDS for helping with stress.
I was also think that instead on concentrating on a big issue like returning to school you could try breaking it up into much smaller steps. Like getting out of the house for five minutes and keep increasing the time. Then move on to traveling on the bus and so on. You can use immodoium to help you through this.