Im sittin exams and im afraid my insides will.......???..............in the middle of the exams?

whenever its DEAD silent in cl, i have to fart (not everyday , but some), and if i hold it in, i fart inside my self........i dont know how to explain it................. in around my inside of my /bladder its rumbles REALLY loud coz i held the fart in...........and im there in cl squirming and tensing up coz its hard work tryin to hold it back and i start sweatin and goin red coz the thought of lettin off in cl WOULD KILL ME!!!!!!!!! what can i eat that wont cause excess gas?Do i have Irritable Bowel Syndrome?