I think I’m the father. It’s been three years though.

About 4 years ago, I had a one night stand. We were both heartbroken and not thinking right. A month and a half later, she told me she was pregnant. I didn’t believe it was mine as I didn’t think I could have children at the time. Either way, I went with her to her first two ultrasounds. At the second ultra sound, they told her she was about 12 weeks pregnant maybe more and automatically I thought the child definitely wasn’t mine. We’d only hooked up about 8-9 weeks prior to this. After that I cut her out of my life, certain that the child wasn’t mine. Fast forward 3 years after the kid is born and I’m laying here thinking, doing the math. Turns out we hooked up September 11th and the kid was born June 15 and now I’m really having doubts about the kid not being mine. What should I do? The woman is in a relationship, we haven’t talked in four years, and she hates me. I feel like I should just leave it alone, but I don’t want to be that absent deadbeat father.