My girlfriend and i had sex on sun 2-5-12. i didn't cum inside her, she took a pregnancy test the following day she got a positive on the test just one day after we had intercourse.

You : You haven't really asked a aquestion, but i assume you're wondering whether a urine pregnancy test would be positive one day after sex. The answer is that a pregnancy would not be detectable that early, so a positive pregnancy test is either a false positive (that is, the test gave an inaccurate result) or the pregnancy is further along than one day. It sounds like you are using the withdrawal method for birth control. Although that's better than nothing, it absolutely does not protect against pregnancy. So if that's been your routine, it could certainly be that a prior sexual encounter between you and your girlfriend--even if you did not ejaculate--could absolutely have gotten her pregnant and could be the cause of the positive result.

Too early : Pregnancy test becomes positive about three weeks after a fruitfull intercourse. A positive test the day after sex is not from a pregnancy from that episode.

Unless : Unless the pregnancy test was read incorrectly, or it is a false positive, then there could be an explanation. A pregnancy test should not come up positive 24 hours after sex. However, the woman may have become pregnant at a previous time. Even if you did not ejaculate inside of her, just the presence of pre-ejaculate could lead to pregnancy.