So the reason why the prince slept around with other women is because the royal family is descended from "Dragon God" that gifts their lineage with massive magical power but with it a huge libido which is dangerous and painful for the royal if he doesn't "release" (they believe it's because the dragon god blood needs heirs to live on), but the prince is miserable because sleeping around isn't pleasurable and it's just a means to an end for him. He sees Lidi (our FL) and instantly imprints on her as his fated "mate", and he refuses to sleep with anyone else after this because he literally can't get it up for anyone else other than her.
Lidi doesn't care that he slept with multiple different women before they met because 1.) she is a reincarnated girl who has had boyfriends before in her past life 2.) her plan to avoid a polygamous marriage was to lose her virginity to a random stranger so who was she to judge and 3.) apparently the prince is so good in bed that she's thankful that he's experienced because of it lol