Ooh I remember this from my first pregnancy, it's actually super normal at 12 weeks, but the twitching and pulsing can be scary when you don't know what's normal! The thing is, sembelit definitely does cause that uncomfortable pulling and crampy feeling, especially around the lower belly and sides, but throbbing in the pinggang area can also just be your ligaments stretching (round ligament pain is real, trust me). A few of us mum friends actually couldn't tell the difference either until we just... waited it out, haha, if it's sembelit, you'll usually feel it more in the actual motion area if you get what I mean, whereas ligament pain is more of a constant ache or sharp twinge when you move. Definitely worth mentioning to your doctor at your next checkup just to be sure everything's good, especially since you're still quite early and want to rule out anything else, they can help you figure it out properly and also give you safe ways to manage sembelit in pregnancy!