Hi, depending on where you are in your ovulation cycle, there is about a 20% chance of getting pregnant from unprotected sex. Ie for every 100 fertile women who have unprotected sex for a month, 20 of them get pregnant.
You are more likely to conceive if you have unprotected sex during the middle 2 weeks of your cycle. You will have the highest risk of pregnancy by having unprotected sex 1 or 2 days before your ovulation starts as per the infographic below, when the ovary releases the egg.
In your case, the risk of pregnancy is lower as your partner did not ejaculate. However, there is still a risk of pregnancy because as you mentioned, penises can leak pre-ejaculate. Pre-ejaculate itself does not contain sperm, but it may pick up sperm from a previous ejaculation as it passes through a man’s urethra. Hence, pregnancy can still happen when pre-ejaculate gets in the vagina or on the vulva.
If you are concerned about pregnancy, you should consider taking the morning after pill ("Plan B" pill) that you can take up to 5 days after having sex, although it is most effective within the first 72 hours.
The sooner you use it, the less likely you are to become pregnant. If started within 72 hours, the morning after pill can reduce the risk of pregnancy by 75 - 90%.
