Aiyoh, this sounds like round ligament pain, lah, very common at 21 weeks when your uterus is stretching like gila. The sharp electric-shock feeling especially when you yawn or suddenly move is classic, and honestly? A few of my pregnant friends had the same thing and panicked juga, but it's usually harmless, just your ligaments being drama queens. That said, since it's happening multiple times, best you mention it to your doctor at your next check-up just to be safe and get peace of mind, they can confirm it's nothing serious and give you tips to minimize the startles (like maybe yawn a bit slower ). Don't worry lah, you're at a normal stage for this kind of thing, but let the doc confirm!