I'm so sorry that I'm just getting to your question.
Yes, your girlfriend could be pregnant. First of all, you already had semen in your penis, and the pull out method is not a form of birth control. Many couples get pregnant using this method.
Since your girlfriend is late she needs to take a test, if she hasn't already done that.
If she's not pregnant you need to use a condom every single time you have sex or she needs to get on birth control. You can google women's clinics in your area. They will give you as many condoms as you want and they can give your girlfriend birth control. There's the pill, the implant, the shot, the IUD. There are several options.
I hope you come back to let me know how everything is going.