Not sure if your paper is plagiarized in any way? Take a few minutes as you write it to run it through any of these Plagiarism checking tools. Each is /are databases that ensure the originality of text by detecting and identifying possible plagiarisms against billions of sources. Products vary by how many uses are free database size.
While there are many reasons which students commit plagiarism, most have this in common: Not enough time was taken to develop a true understanding of the subject so as to describe it in your own words, and racing to meet a deadline before your work is fully baked. Judgements are rendered regardless of reason.