Nsfw pain

Hi guys , so I was bent over but standing up and my pelvis area started hurting so bad. I kept saying how multiple times loudly. My bf stopped what he was doing and asked what's wrong and if I was ok and if the baby is ok, were guessing it's fine but does anyone know what just happened? I've never had that bad of pain and it's not happening now that I'm laying down but it scared me for a minute