few cm of penetration, few seconds without ejaculation--preg

my boyfriend masturbated last night without urinating after that..early this morning, he tried to penetrate me. he was able to insert his penis for a few seconds but only a few cm. now we are afraid that i might get pregnant because of precum. i am fertile at this moment because it is 14 days after my period. i washed immediately to remove any sperm present but i know i can't wash off sperms that were left inside me. what is the probability that i might get pregnant? please help...