I'm sure this question is a duplicate, but I can't find it, so I've answered it.
TL;DR: The historic singular "you" was lost and plural "you" took its place.
Early Modern English had singular "thou"/"thee" and plural "ye"/"you". Plural "ye" was also used to show respect to a single person, as "thou" was a term of familiarity.
"thou": singular and familiar;...
Yeah, you've hit on a weird quirk of English grammar here (modern German does similar things, I think).
You have three ideas here.
1) Pregnancy has stirred up feelings.
2) The feelings existed.
3)I didn't know that fact.
Combining the last two, you get
"I didn't know that the feelings existed."
You can leave out the subordinating conjunction "that" in ...
The subjects in the sentences are people, traffic, you, and you, in the respective order.
It is just that the sentences’ have been written in the interrogative form which doesn't mean they have no subjects.
You have x number of children.
Yes, you have…
No, you do not have any child/children.
Have you not (haven’t you) any ...