Hi!
If your girlfriend was my patient, I would advise you two that it is pretty unlikely that she could become pregnant from this scenario. Nothing is impossible, but I think you are probably pretty safe. ALSO--there is emergency contraception available (if things proceed)--there is "the morning after pill" which she can take. It is available at most pharmacies. She would need a prescription if she is under 17 years old--but it is better than pregnancy!
Good luck!
Dr B
Nope. Semen would have to be inside her vagina for even the slightest chance. But I will advise you to be more careful! One thing leads to another, you know. Please talk to her about your contraceptive options, be it condoms, the pill, anything but the 'pull out' method because that isn't reliable. It's not going to be the easiest conversation, but if you think you're old enough for sex you should be old enough to have that conversation.