I don't know exactly when I ovulated and I am someone who tends to have irregular periods. If my due date is December 23 based on ultrasound dating, most likely when did I ovulate. My lmp was march 7, 2017. I usually don't have 28 day cycles and sometimes they can go as long as 50-60 days. I slipped up guys and slept with someone unprotected on the 23rd of march! While having sex the day before and after with my partner (please don't judge me for I know what I did was wrong) the guy who I had sex with is claiming he can't have kids and he has a low sperm motility count of 25%. I'm really just tryin to rule him out. The online calculator puts my ovulation date at/around April 1-2... so would sex from that date with HIM make this pregnancy viable? Or would the only way to tell is to take a prenatal DNA? I need to know before I get any further along in my pregnancy. It's not fair to my partner.