When did I get pregnant?! Details; Last day of ovulation was May 5th, a day I happened to have a one night stand, no protection, and he did not ejaculate in me. LMP took place May 10th through May 16th, had unprotected sex with another guy multiple times after the 17th a few times. I'm 18 weeks and 1 day pregnant and my due date is February 21st, 2016.