sex and babies 👶🏽

ok so I’m shy about writing this that’s why I’m posting anonymously... but everytime me and my boyfriend have sex after he is done nutting inside me most if it comes out and we both figure that’s why I can’t get pregnant 😔 but I don’t know. I want ONE kid for right now as the moment but can anybody help me understand this and why it is coming out ? I want a child but obviously all his juice is coming out 😖