As to Elizabeth, that is indeed conjecture, BUT that is why I used the phrase "I think" and the word "perhaps". However, if you look at her life and choices objectively and read some of the available biographies, you will see that she planned her latter two pregnancies, spent a significantly greater amount of time as a hands on mother with those two children, and by many accounts from those who saw her in both public and private, was much more comfortable and happy as a mother with them than with her older children.
And no one said she did not want to marry Philip. She very much did. In fact, early on, her parents were not comfortable with her infatuation with him as she was very young when it began. Not wanting to be a mother immediately does not mean she did not want to marry. And Charles was born just short of a year after their marriage.
BTW, do you seriously believe that everyone who is in love with someone automatically wants to have children with them? That is far from the truth. Many people have little or not desire to be parents but that does not mean they do not love their partners. Also not wanting to be a parent immediately on marrying or at a very young age (22 for Elizabeth) also does not mean you don't want to be a parent at all.