Help!

Girls! I am trying to get pregnant and I literally have only let my bf finish in me, any other partner I’ve had have used condoms. Anyways, when he finishes in me.. I feel like all of it comes back out.. I don’t know if I’m doing something wrong or if it’s normal.. and I’ve been trying for a month to conceive but no luck yet so that’s why it also makes me think that we are doing something wrong! Also i have had some of you girls tell me to try and lift my legs up so that the sperm can travel. But we are all over the place we start in our bedroom and end in the kitchen lol! I need advice!!