this is one of the debates on this thread - i.e, is the noise caused by anxiety or not?
I've probably written it somewhere a few months back - but my situation re how the noises started is almost exactly the same as yours. I was sitting in an exam in 2nd/3rd year uni and my stomach made a noise and I remember thinking, 'what was that?! Never had that before!' Fast forward a year on from that, and I was in bits going into every single exam - purely because of the anxiety of getting the noises.
It's funny, I think in the 50 exams I did in college I was in that state for at least 35-40, and if the noise then ever did happen - it was brought about by the terrible anxiety I had of getting the noises. So, a vicious circle - as I'm sure you know well.
I get the same tightening up of all the muscles and the bouts of mainly getting overheated. The exams were always hard going because of this - the mix of anxiety and adrenaline always leaves me feeling very exhausted.
Take last night - I went out for dinner and then to a classical concert - the sound levels of which varied from: every now and then being fairly loud - to 10 minute pieces of dead silence - with not a noise coming from the 1000 people in the hall. Inside, I was a wreck - but I kept steady breathing - and kept trying to follow the music because I find that when I'm not thinking about my stomach, I'm ok.
For the first half, my stomach made no noise - despite my overheating! Then 5 mins into the interval - with no one around - my stomach made noise - so I went out and sat on the toilet for a few mins - and then came back just as the orchestra was about to start again. The second half was the same thank God, and I was counting down the minutes. Then the final piece of music turned out to be a loud, rousing performance and I knew I was home-free!!! I get a real buzz from doing things like this, as I feel like I've won or something. In fact during the whole performance, I did hear a few stomach noises - but none were from me - and it made me feel better

Everyone has them you see, and not one person made any comment about whoever's stomach was making noise!
Today though, I feel so tired. I'm an amateur runner btw. I run every distance from 100m to marathon - and I can tell you - purely because of the anxiety/adrenaline I felt last night - I feel every bit as tired today as I would have had I run a marathon yesterday. So, don't be too hard on yourself.
Exercise, whether its running/gym/rugby etc. gets me through the quiet situations. Myself and "Matt_User" (I think it was) have noticed this before that - say you do some hard exercise for an hour or two - for the next few hours that follow this - you will almost always get no noises at all. So, before every exam I did with this condition, even if the exam started at 9am, I used to go running at 8am! And it almost always worked. 90%!
Its the same for me and meals out. I can be around people for the whole day or whatever, then as soon as I sit down at a table - where I'm expected to remain for the next 2 hours or whatever - I feel myself overheating - even before the food arrives! I often have the same toileting situation - but I'm much better now than I used to be, but it's more through experience than anything else - E.g, I don't eat a lot anymore - and my diet is very fussy - I will simply refuse to eat certain things. I also don't drink any alcohol anymore. At all. Ice cream seems to do bad things to my stomach!!
but anyway, like the exams and anyother impending quiet situations, I do exercise before them. I don't eat for hours and hours before them either so that when I do go in - I'm generally starving! I think at that point, my body is too busy repairing itself from the exercise I've done to make any noise! Also, I'm starving - if there's any noise - it's legit..! I generally find that the hot/cold feelings come more when I have eaten - i.e, not when I'm hungry btw.
Anyway, I haven't posted here in a while so there you go! I hope at least hearing others in the same boat helps! If exercise is an option for you - by all means take it.
My own belief on the noises is that it is caused by anxiety - whether conscious or not. My whole life I have been pretty hard on myself - even as a child if I didn't get the best result in anything - that was the end of the world - and as a result - I was under a lot of pressure. I reckon I put myself under too much pressue and something has *broken* - maybe not physically - but mentally - whatever is causing the anxiety I mean!
But as help_wanted pointed, out there are other arguments for the noise too. Indeed, I could be sitting at my desk at work with no one around and nothing on my mind - and a noise might sound. Do I feel anxiety then? No. But... I believe it is a result of whatever has been *broken* before..! It's a tough one to figure out.
Re the test/medicines that people have mentioned. I haven't done any of them and never will. For me, the best thing I can do is learn new ways to deal with it - whether through exercise or diet - which has helped me a lot. Of course I keep one eye on everyone else's progress because if someone finds that miracle cure - well, frankly, I want in!!
Anyway - hope everyone's doing well! Best of luck to one and all!