leftover sperm from where? did he already had sex recently before this? it is after you start to have sex that he gets turned on and produces the pre-ejaculate fluid which can actually have enough sperm to make you pregnant. then as he continues a bigger quantity of liquid finally squirts out as he climaxes at the end. so yes you could have gotten pregnant from that risky act.
could i have gotten pregnant if before we had sex my partner peed to wash out leftover sperm/kill it?