body can't stop vibrating

My whole entire pelvic region is vibrating/fluttering. I know it's ultimately being caused by a muscle spasm but I don't know which one. It's not my uterus because I've felt that before & when my muscle usually twitches I can physically touch it & see it twitching but I can't feel or touch this one, which is why it's difficult for me to locate. It feels like it's behind my uterus and near my intestines but there aren't any muscles in that area. Then again it feels like it could be a muscle in my butt but because everything in this region is closely knit, everything feels the same. It's just super annoying because it's literally vibrating like a muscle twitch does but just keeps on spasming! It's super annoying 😓