Question about the term! I'm confused how to count! I will try to expl…

Question about the term! I'm confused how to count! I will try to explain my thoughts! Currently, it's 14 weeks and 4 days! That is (these 14 weeks are whole, they have passed, so it goes in essence to the 15th week?! And December 2nd according to the calendar is the 15th week, but in fact it turns out that 15 has passed and the 16th has started instead of the 15th?!! I am very hopeful that you understand what I want to say, I don't know how to explain it any other way... I'm completely confused on how to correctly understand my due date