I feel everyone's pain here. I suffer from the same problem. My friends laugh at me when I tell them, and some actually think there's something wrong with me

I don't know what it is, and it's silly to think it could possibly be something severe enough to be diagnosed. I thought it was just me, but I'm happy to know that there are people that also hate being in a quiet room full of people, whether it's during a lecture or worse, an exam. I've had too many traumatic, humiliating experiences, especially in small classrooms, to date because of this problem.
I notice it most frequently occurs right before an exam, presentation, or when I know I'm going to be in a quiet area with people around. My hands get clammier than they usually do, my stomach starts feeling uneasy, and I get very tense and jittery. The anticipation, nervousness, and anxiety get to me and in my head, I'm always hoping that I don't make any funny noises or look so obvious.
Through my experiences I've learned that holding it in is the worst thing to do--no doubt about it. I've used Gas-X before, but that didn't work so well (I should have used their ultra-strength instead of the regular one), plus I feel embarrassed purchasing it in public or keeping it in my bag. So I've found 3 ways that are most effective in dealing with my curse:
1) Watching the foods I eat, i.e. the day before a test. I don't eat foods that I know would make my stomach bubbly/give me gas. I avoid meat and especially anything lactose (I fear developing osteoporosis later on in life because I can't drink milk everyday

Lactaid still makes me feel bloated. Any suggestions?), and stick to fruits, salad, soup, simple foods, and small snacks. This has helped me prevent having another embarrassing story to tell.
2) Carrying around a sweater. Yes, this is random and sounds silly, but it's one of the most discreet ways I can deal with my problem. Most of my mortifying moments apparently happen on hard surfaces, like wooden or metal chairs. My bag can only hold so much and I'd rather not put it on the floor, so onto the chair my sweater goes! You don't know how comforting it is knowing that it's there to "save me" when I need something to suppress any funny business that goes on behind me.
3) Going to the bathroom. I practically know where all the bathrooms are on my campus. Sad, I know! But really, having a clean system can be a source of immense ease.
I hope these tips will somehow help you as they have done for me. You're not alone!