Confused!

I don't want to sound stupid but I'm 19 years old. My boyfriend of 3 years wants to have a baby. So we decided to try. About a month ago, maybe a month and a half ago, we tried and he came inside of me 3 times in one night. All at different times. But I never ended up getting pregnant. Is that normal? Or is there a reasoning behind it? Because I've been told I could be unable to have babies, but I've also been told that it was just a whatever thing and It just didn't work that time. Anybody have any explanations?