Dear johnny,
i got my first period at 13 but it never became regular until I was 16 years of age. Does she ever have regular periods normally ? If you wore a condom and your sure it never broke then she won't be pregnant. I mean you wore a condom and pulled out when you came, so it would have to be a miracle for your sperm to get through the rubber. If you are both concerned about it, there are places you can go together and get a pregnancy test or simply buy a test from the supermarket or chemist, that is the only way to know for sure and put your mind at ease. In the meantime, maybe you could suggest she starts a course of birth control pills now that you are both sexually active. By the way, good on you for using a condom and also for coming here and seeking help. You sound very responsible, your girlfriend is lucky to have a caring person like you in her life.
Regards,
.::suzy::.