chances of being pregnant?

So I wasn’t too worried about the one time only unprotected sex (we both want kids and are in late 20s so we aren’t against it) but then I looked at my ovulation calculator and it’s becoming all too real!! So my boyfriend and I had sex for 5-10 min without condom. Then stopped and I finished him off with oral sex. I really should have used condom since I just started a new birth control and it’s only been a couple days since I started but we chanced it for 5-10 min. Well the next day I look and my ovulation calendar says it was my most fertile day of the month 😭 mind you I have had a spot on regular cycle for about 7 years. I’ve never been pregnant so what exactly are the chances of getting pregnant from possible pre cum? And it if happens did I just pick the perfect day to do it or what??