This past week or so I became sexually active. My boyfriend and I were doing quite a bit together, but during his visit my period started. On the third day of menstruation we decided it would be ok to have intercourse and he did wear a condom.However, when he withdrew, he said that I'd been so tight that the condom had slipped down on his penis a bit. He did not ejaculate in the condom, but there was evidence of precum. I just want to know what the chances of pregnancy might be. I have not taken plan b and I am not on horomonal birth control.Thank you.