Rubbing my penis on gf's vulva.3 days after her last period, I didn't ejaculated. There may be precum. She washed her vulva w/ soap after. Preg chance?

No. Conception (pregnancy) requires the sperm in the semen, and sometimes also present in the precum, to come in contact with the cervix/uterus during the 3-5 days preceding and around the time of ovulation during mid-cycle. Safe sex always recommended to prevent both an unplanned pregnancy and being infected with an STD.