I slept with a woman who was on her period. We slept together between the late hours of November 30th and early hours of December 1st. The first day of her last missed period was November 28th. She stated at the time she was on birth control. I honestly don\ t remember if I ejaculated inside her or not. On January 10th, she told me she did not have a period and a pregnancy test came back positive. We went to have an ultrasound done on her on January 13th. The doctor that did the ultrasound said they date it back from the first day of the last missed period, so she is 6 weeks pregnant, even though they stated, it is unlikely she has been pregnant for the entire 6 weeks. She stated initially to me that she had unprotected sex 10 days after we slept together with someone else. However, later she stated that they wore a condom and she was lying about it being unprotected. She stated she was sure it was me based on the fact that she was 6 weeks pregnant. What are the odds it is mine? Here is some additional information I should also state that she may have slept with one other person in addition to the person 10 days after we slept together. It is also worth noting when we slept together on November 30th there was tons of blood on my sheets left over, afterwords. Lastly, the doctors office that did the ultrasound told me that they have a chart that states when she likely became pregnant, and they said it likely would have happened on the 16th-19th. Not sure how accurate that is. I d like to know what the odds are, it is mine, given she was on her period, as opposed to someone else 10 days later, with a condom, or without one seeing as I don t know if she is lying or not, and just any helpful information. She is 19. I am 27.