Is It Possible My Girlfriend Can Get Pregnant?

I would say there is a very very very small chance that she's pg.

*disclaimer - I do not condone the using of the following information to justify risky practices such as pulling out as sole method of birth control*

you need millions of sperm to get preg. Yes, in theory it is only one sperm that reaches the egg, and it's theoretically possible for you to get pregnant... Very very unlikely. Men who only have a sperm count of a few hundred thousand or even several million are often unable to have children because while many people will tell you that sperm can live in the body for several days they are only partially true. The environment inside the vagina is acidic and very hostile to sperm. Millions of them die instantly, the dead sperm then create a kind of wall around the live sperm protecting them. The longer they are there the more die. On the approximate 2-3 day journey to the egg only a few thousand out of the original approx. 100 million will get there.

So i'd say no - your gf is not preg. But still - be careful, and educate yourself about the risks before you engange in more risky behaviour.
~ laura