I've been there. My first year of college I suffered from this awful cycle of diarrhea and constipation. I had a huge fear of pooping anywhere but home. My doc said I had IBS and I now realize it is from stress. Now when I get panic attacks, I have to go #1 and #2 after. Every body responds to stress differently. And when you are nervous, I guess your colon just spasms. Do you eat enough fiber and all that?