she mite just be late cause of her thinking she mite be pregnant!!!! but if you used a condom and she is pregnant then there is a 50/50 chance that it could be your and if the pulled out to cum in the condom there is like a 25/100 chance!!!! i have known of a girl once before to get a condom and poke holes through it so she could get pregnant and it did work!!!! and if she wanted a baby by you and didn't want to tell you(thats what it sounds like) she would do bout the stupidest things to make sure your in her life forever!!!! or maybe she mite be cheating on you but don't ever said it's not yours til a result proves it wrong cause you don't want to look crazy when it does come out to be yours!!!