I have a question.

I was seeing a woman who is not pregnant but she had been seeing someone else too. She doesnt have an ultrasound done yet so I am only going off what I know and I wanted to ask you to see what my chances are of being the father.

She was seeing another guy in March, she claims she had her last period around march 26 or 27 and she again saw him on March 30th and supposedly that was the last time she was with him. I saw her the night of April 14 or the morning of April 15th. I used protection but inconsistently and did not ejaculate in her but I did in a condom. I was also with her April 17 and 22. Now when I was first with her on April 14 or 15 she told me she was finishing her period then for some reason. However on May 2nd she took a pregnancy test for some reason and it was Positive. She took the clear blue pregnancy test which has a week indicator and it showed 2-3 weeks. Im not sure how accurate that is. She tells me the period she told me she was having before April 14 wasnt legitament and that her real period starter March 27. During the week of May 2nd she was having cramping, and bloating. Note this is roughly 2 weeks after my initial encounter with her. Im not sure how much her dates are true or if shes is honest but based on these dates to me it appears unlikely that she conceived on April 15 and the period she though she had before could have been pre implantation bleeding but I dont know. She is due to get an ultrasound on friday.

My question is
What are the chances Im the father? and if she takes an ultrasound on May 13 how many weeks would she have to be to exclude me?

Thank you.