Both were naked. my bf was masturbating and he ejaculated over my thighs and the top of my vagina.. i washed asap. there was no penetration. need ecp?

Not likely: First, you should ask yourself whether it is your "fertile window", which is ~3 days before and the day of ovulation. If not, diminishes the chance of pregnancy to almost nil. Otherwise, the chance of sperm reaching the cervix from outside the vagina where ejaculation reportedly occurred is still highly unlikely especially since you washed the area asap. Doubt ecp is necessary.