Can my gf be pregnant?

Ok so we have been dating for 6 months and we recently decided to have . She was a virgin and so was i...so this past tuesday i went to her house and we were gonna have . My underwear had some pre *** on them . When i decided to put on the condom i did ..but the thing is that i left them on while i was going to enter her..so some pre *** may or may not have gotten on the condom ..i realized my mistake today ..when we were gonna do it again...this time however i didnt do the same ..also i never eajaculated cause it was hurting alot for her..im 17 and she is 15 and i am really scared because im not ready to be a father yet. So basically i was wearing my underwear with some not alot of pre *** on them while i had the condom on...can she get pregnant? What are the chances ? I really need help .