Genital rubbing, pregnant?

Last night I had leggings on. I was with my boyfriend. I had the leggings on the ENTIRE TIME. Never pulled them down. BUT, he took all his clothes off, so he started rubbing his penis on my vag (I STILL HAD MY LEGGINGS ON), and I felt his Precum. Could I possibly become pregnant over this?! Should I take plan B?!? HELP.