Trying to conceive

Hi guys, I'm new to this group and I wanted to introduce myself. My name is Christina and Ill be 19 next month. I have been with my finance for 3 years and have been trying to conceive for a while but I don't know what I'm doing wrong cause I keep pushing all his cum out. And when I try to lay down for a while and then get up it comes out no matter how long I lay down. So if anyone has any tips for me to get pregnant I would appreciate it. Thanks(;