My girlfriend and i had unprotected sex last night. i didn't come inside and it lasted about 5 minutes. what's the chances of her being pregnant?

Think about Plan B: If you want to avoid pregnancy, your girlfriend should consider emergency contraception. You can get pregnant from sperm on the penis prior to ejaculation regardless of the length of intercourse.

Pretty good : Use over the counter Plan B if intercourse was within 72 hours to decrease the risk of unplanned pregnancy. Its over the counter. In the future you need to use condoms. She should start birth control also.