Is this even a possibility of pregnancy?

Okay, I gave my boyfriend a hand job yesterday, he never touched himself but immediately after he fingered me. I just have this lingering thought in my mind of WHAT IF he did get some on his hand. Keep in mind he had his pants on the whole time and i was in a dress. The only way he could have even come close was when he buckled his belt. Even if he did...aren't this chances extremely low/impossible, especially since i just finished my period a day ago? This is as far as we've ever gone and trust me, we're old enough. Thank you for any help, please, no judgment