Aahhh mine used to do that too!! I tried everything to cure it but I noticed that eating a big breakfast helps an having a small snack if it begins. It feels like your eating too much but you can always exercise. I hope this helps bc I know when it happens it is embarrassing especially if in a quiet room with people
could be gas as I also suffer from this but its more of a bubbling not rumbling. need to figure out what foods cause this and try to minimize consuming them. as far as nervousness making it worse could be a coincidense.