Hey, I Got With My Girlfriend Around The 9th, She

Hey, i got with my girlfriend around the 9th, she just come straight out of a relationship. We first had sex on the 14th. We are now pretty sure she's pregnant. What are odds the babys mine? Shes complaining her boobs are hurting alot. She took a pregnancy test and there was a very faint line.

Thanks for any help in advance