HELP PLEASE! Is my girlfriend pregnant?

Hey, I'm one of those stupid teens who just couldn't stop their hormones but luckily I realized what I was doing and stopped. On saturday my girlfriend got on me and I was in ehr unprotected for probably 20 seconds max, I know time doesnt matter but I'm just pointing this out. I didn't ejaculate in her but I did much earlier in the day but urinated after that a few times. Anyways her last period started may the 4th and she says she is most times a day early but she doesnt have very normal times. So today is 28 days later from her last period and she didnt get hers yesterday adn today she said she felt a little stomach sick but the flu is going around. So I was just wondering if anyone out there can calm my mind and tell me what could be on the go? And also she could be stressed out because exams and alot of last minute work, test and projects in school. Anyways please answer to this question on what you guys think of this like is it very likely she is pregnant or what? Thank you alot guys, I really appreciate it