Leaving in semen after sex

Are you supposed to leave semen inside for a while after having sex when trying to get pregnant? Like do I need to lay down and elevate my hips and all that jazz? Or is that a myth? My biggest concern is that I get UTIs very easily. I have to pee right after sex, or I will contract one. So, how do I do both? Help a girl out 💁🏻😅 #ttc #