First time, no condom??

Hi! So last night my boyfriend and I (ages 16 and 17, respectively) had sex for the first time! We kind of just wanted to see if/how it would work, and what it felt like. And even tho it was just a "trial run," it was lovely and I love him so much for choosing to lose our virginities together. ❤️
He was only inside me for like, 20 seconds. We stopped because we didn't have a condom. My calendar says I'm on the last leg of my fertile window, and the only fluid he could've put in me was a little bit of precum. But still, I'm kind of freaking out. I'm not going to get pregnant, right? What can y'all share about your first times? Calm a girl's nerves, please!!