drop in the pit of my stomach

[Ronhool]

Could you tell me what the phrase "drop in the pit of my stomack" means?
I know that "in the pit of stomack" means "под ложечкой", but what other variants could be? Frankly I don't like
the russian phrase "под ложечкой" and don't hear it much.
The context is following:
In between those two parts, I will ask that anyone who is shopping the class and would like to leave at that time do so then. I would be grateful if you would wait until that point if at all you possibly can. It just makes the whole thing work a little easier and it prevents that drop in the pit of my stomach when I see half of the class leave.
Между первой и второй половиной лекции, я попрошу всех кто еще выбирает на какой курс записаться и хотел бы уйти в это время, так и сделать. Я буду признательна, если бы вы подождали до этого момента, елси вы конечно можете. Так просто все будет немного проще и "не ранит мое сердце/у меня не засосет под ложечкой", когда я вижу, что половина класса уходит.

What a good russian equivalent would you suggest?

Thank you in advance.

[Ronhool]

Maybe I put my question obscurely. I just want to know what the word "drop" in this phrase means?
If I am still unclear, let me know please.

[ibelk]

Похоже, только носитель может ответить. Возможно, это "самопальна идиома".
В словарях можно найти определения и примеры:
1) If you have a feeling in the pit of your stomach, you have a tight or sick feeling in your stomach, usually because you are afraid or anxious. (CollinsCobuild)
2) the part of the body in which people say they feel fear or nervousness:
I got a sick feeling /a knot/ in the pit of my stomach when the news of the attack was announced. (CALD)

Отсюда примерно-дословный перевод:
drop in the pit of my stomach  = чувство, что что-то оборвалось у меня внутри и упало в желудок, вызывая ощущение нервозности 
[Drop могло быть навеяно выражением My heart dropped.]

Вообще, по-русски преподаватель выразился бы совсем по-другому, так что, по-моему, не так уж и важно точно сказать, как в этом случае перевести слово drop.

[Gold Leaf]

In this context "drop" means "that sinking feeling".
I have to say that I have never seen the phrase "drop in the pit of my stomach" used before, but it is understandable as "drop" and "sink" both express the idea of falling or lowering.

[Ronhool]

This phrase was taken from the lecture in Yale "The American Novel Since 1945 with Professor Amy Hungerford".

[asil]

This phrase was taken from the lecture in Yale "The American Novel Since 1945 with Professor Amy Hungerford".

Вы не могли бы сначала определиться что Вам от нас хотелось бы получить. В самом первом сообщении Вы просите точный перевод (кот. я не знаю), а потом просите об'яснить что имеется в виду.
Если требуется понимание, то Gold Leaf уже об'яснил.

[Ronhool]

Thanks to everyone, now I understand.

"I have to say that I have never seen the phrase "drop in the pit of my stomach" used before"
That's why I pointed that this phase was taken from leture.

The question is settled, thank you again.

[nas2000]

Doing a city tour in Nashville one day I told the people on the bus about the Maxwell House slogan: Good to the last drop. One smart guy in the back yelled to me that it wasn't about coffee at all. It made me nervous, I opened my bag and showed him the script. He smiled and said he was just kidding. Can anybody guess what he meant?

[ibelk]

Doing a city tour in Nashville one day I told the people on the bus about the Maxwell House slogan: Good to the last drop. One smart guy in the back yelled to me that it wasn't about coffee at all. It made me nervous, I opened my bag and showed him the script. He smiled and said he was just kidding. Can anybody guess what he meant?

http://www.urbandictionary.com/define.php?term=last+drop
meaning 5?

As for myself, if you hadn't mentioned coffee I would have taken the slogan as advertising of some strong alcoholic drink. 

[nas2000]

meaning 5?

No, no, no, no... It's an old elevator.

[ibelk]

So, it's black humour.  Somehow, it reminds me of the old anecdote:
At the top of a bungee jumping tower a visitor asks the attendant:
- How often do you change the elastic rope, I wonder?
- Oh, quite often, you know. Every time it breaks.