It Hurts . 🤔

Okay , so me and this guy have been sexing for a very long time & Saturday , while we were having sex , I got a sharp pain in my lower stomach and back and ass area , I wasn't sure why . And then yesterday , it happened again . When we start off I'm fine , it's just like 15 mins into it like right before he finishes I start hurting . Any advice on what it could be ? 🤔