Stomach pain during sex?

Emmi
Was just having sex with hubby and I was on top. I'll be 24 weeks tmrw and I started getting a weird pain in my gut on both sides of my stomach in the middle of sex. I'm thinking it was like my uterus cuz that's a little lower than where they say the top of my uterus is. Really weird cuz it hasn't happened during sex at all while being pregnant. Anyone know what's up?