This is indeed a big thing for me, too. I find that my worst triggers are when I am with a crowd of strangers. I think: What if I have a panic attack? I will look really stupid and probably faint and throw up in front of everyone. How embarrassing. Of course, this just leads to me being worried about it and any bodily signal that I have, I fixate on it and start to get worried - snowball effect!
The closest that I ever came to "losing it" and looking really embarrassed was when I was on a skytrain. It was SUPER crowded and I barely had room to move (was standing up). I started to hyperventilate and had to get off that train NOW! I was fidgeting all over the place and finally started to tell my husband that "I have to get off. I can't do this." A guy next to us eyed me, but what I saw was not ridicule, but concern. The kindness in his eyes was very reassuring. Then at the next stop (the one I was sure I was going to flee at!), a transit officer got on. She asked everyone to move back. I told her that I HAD to be by the door because I was feeling claustrophobic. She said "okay" and chatted with me for a while. It really took my mind off of it and I rode that train all the way to my destination without getting off!
So, the lesson learned was that even if we DO end up looking "odd" to those around us, more often than not, people will not be repulsed or critical, but will actually want to help. They are sympathetic and probably have issues of their own. Think about it: if you saw someone who was obviously going through some distress, you would be willing to help. Most people are like this (well, one or two at least! :-) )
So, no - you are not going to lose control, even though it feels like it
Even if you "come close", you will not embarrass yourself. We all go through stuff as humans and all those people around us aren't perfect. They're working through things, too.
So, Tin Tin, you are not alone in feeling that way. It is such a derailing kind of feeling, for sure, but it will get better and each time you prove to yourself that you are not losing control, you are growing stronger, I feel.