Is it normal for,,, and how do you prevent...?

It is normal that it leaks out, if you are trying to get pregnant put a pillow under your butt to raise you up to help his sperm swim to meet the egg and when he ejaculates it is up to 40 million sperm if he is fit and healthy. It wont matter if it leaks as this is only fluid to help the sperm get into you and by the time it leaks out the little swimmers are on their way. Good Luck,