Trying to get pregnant

My boyfriend has no kids yet and we are both 26 years old. I have two kids of my own. The problem is that he said he thinks he can't have kids. He doesn't want to go see a doctor to confirm if he can't have kids for sure. I'm mad at the same time because I love him and I really want to try to have a baby. Get pregnant was never a problem to me. I've been having sex with my boyfriend for over a month and nothing 😔. Can anyone give me tips or advice on how to help him and me get pregnant soon. Thank you.  
P.S he really wanted to become a dad soon. He's trying.