I've actually been in this situation in high school before. For days I had to present in front of my class, I would always get serious urge for diarrhea due to nervousness. In one presentation in senior year, it got so bad that I had to squeeze my buttcheeks like my life depended on it simultaneously while trying to act cool giving the presentation. No idea how I made it out of that without shitting my pants explosively. Literal out of body experience.