Hi Zion I think the chances of you being the father or any child i this instance are fairly slim.

She may not be pregnant at all. If she is indeed 2.5 weeks late, she should do a test and find out for sure.

As for the withdrawal method - Spring is spot on! How many other guys is this girl sleeping with - unprotected?? Herpes, hepatitis, HIV...there are several STIs you could now be carrying around with you too - I certainly hope you aren't having unprotected sex with anyone else!
Seriously, have a hard long thin about 2 things - 1. why oh why are you sleeping with a girl who is sleeping with at least one other guy (do you like sloppy seconds??) and 2. why on earth would allow yourself to risk getting someone pregnant and contracting a very serious disease yourself?

Sorry if that sounds like something your mum would say, but seriously, you are talking about a girls life, and the life of a new human being. How that life comes into the world is important and deserves more than your casual post-coital concern.

Good luck, I hope you can find yourself a steady girlfirend who isn't sleeping with 5 other people.