How To Determine The Father Of An Unborn Child Using Last Menstrual Cycle?

I have a question. I had sex with a girl in the middle of august 2014. Just now the girl contact me saying she is pregnent but doesn t know who the father is and said it could possibly be me. Her due date is July 3rd 2015 which would make it about 46 weeks after we had sex. She said something about her pregnancy being messed up in the beginning so it be longer. But as of now she says she 24 weeks pregnant which would take it back to her having sex at the end of September 2014. Since the dates don t add up but she s saying it could possibly be mine because she has no sure fact who the father is would it make sense for me to believe her as she just contacted me now or would it not be possible that it is mine? Thank you and please get back to me.