Hello dear Understand your concern Yes pre ejaculatory fluid can cause pregnancy as it contain sperm but sex should be done in fertile phase of cycle. So good decision taken by you as you took Plan B tablet. There are two reasons for white discharge after taking Plan B pill. 1. Preparation for withdrawal bleeding: As plan b contain high progesterone and cause white discharge and withdrawal bleeding. It is normal and goes off with in 3-4 days. Maintain pelvic hygiene by using V vaginal plus wash. 2. Vaginal infections: bacterial vaginosis, chlamydia, gonorrhea. All are sexual transmitted disease and should be rule out by vaginal swab test, urine testing and STD screening test. It should be treated by proper antibiotics. So consult the gynaecologist and take proper treatment if discharge will continue after 4-6 days. Hope this may help you Best regards Dr. Sagar