Heavy making out?

So I was with the boyfriend earlier, and we were kissing. Like, kissing kissing, roaming hands and all up on each other kissing. At one point, I spread my legs (I was wearing my school skirt) and pulled him up against me, and we stayed like that for a while.

I was thinking, could the panty-to-trousers contact cause pregnancy if prolonged? Is there a chance of any fluids coming into contact? Like I know that sounds stupid, but I've heard of girls getting pregnant, like, fully clothed.