Me And My Girlfriend Had Sex Today And I Did

Me and my girlfriend had sex today and I did not use a condom how ever I did not ejaculate in any form. Meaning I did not pull out because I never came we were out of time and needed to leave so we stopped I know that there is a chance of precum getting her pregnant and I masturbated the night before do you think we need to buy a plan b? Also note that we are 17 I'm not sure how fertal I am and what not.