My man, if you are asking question like this, it is time for you to stop having sex. If you don't want a preganancy, you should educate yourself. You do not talk about using condoms from your post, so I suppose you are having unprotected sex as well. I am sure you trust your girlfriend, but if your lack of knowledge about pregnancy is such, I suppose hers is the same. You do not have to have intercourse before enough semen can leak inside her. Sperm is carried by Semen. So the answer to your question is Yes, she can get pregnant this way. You are only 19, don't rush. There are tons of books and videos for you to watch together so you are both smart and you have all the time in the world, but if her cycle has not started, you may want to get a pregnancy test from any drug store. You don't need a prescription for those. Be careful not stupid.