Am I Plagiarizing?

After reading all the article about plagiarism on the website of Harvard University, my mind became in limbo. My mind just got stuck and wondered if  I were guilty of plagiarism for all those years.

(Image from https://www.paperrater.com/page/plagiarism-detection)

I became to realize that all those words and ideas that I wrote and expressed might not be my own. All the thoughts, reflections, insights and realizations might belong to someone else. Worst, my knowledge that I acquired could be taken away by those who put them on my mind!

And this thought came to my mine - if plagiarism if copying verbatim someone else ideas or a portion of it in writing without citing the author or source, what do you call it when you express them verbally? If such is also illegal, do we have to cite the author or the source whenever we speak? If such is the case, all what we say will be full of citations.

Can we say that what we learn is our own? If not, how and when we know that all these ideas are common knowledge that need not be cited? If a mother advised his  son to do something nice and the son obliged, should the mother cite where she got that idea? If the son said that to his future son, should he cite his mother or the source of his mother where the original idea came from?

If we copied an idea or expression from an author who copied it also from an author who copied it from the original author, shall we cited the author whom we copied the idea or the original author whom we never read his original writing?

Since new ideas are rare, we are bound to be guilty of plagiarism. What we write and say might be someone's else idea? What if you write aimlessly without referring to any form of media (like what I am doing right now), am i plagiarizing if those ideas were already written by somebody else?

What and how we know that an idea is common knowledge or not? Who decides that an idea or expression is an original one and must be cited? Is there a maximum period that a work, idea or belief be considered of public domain and should not be cited?

Well, those are some thoughts that I need to address before writing. By the way, what I 'm writing  right now might  belong to somebody else.  Oh, am i plagiarizing?