Help or Info please

Hello ladies, I have a very important question that needs an answer.... I had sex I am 18 and although he did NOT cum in me... how likely is it that I will get pregnant from precum... I read online it's highly unlikely but I don't know. I am worried because I was fertile during this day and I AM NOT READY FOR KIDS... maybe I'm paranoid but I need to be sure. Can anyone give me advice.