precum

ok so what are the chances precum will get you pregnant? before my bf inserted his penis in me, I gave him a bj to make sure there would be no precum goingn in me. my period's almost late and his penis was only in me for a split second. we didn't go any further and we agreed to never have unprotexted sex again. we haven't any intercouse after that split second. could I possibly be pregnant? I've been very stressed lately and idk whether that's causing my period to be late or pregnancy..