Sakit pinggang sebelah kanan masa pregnant memang biasa, especially sekarang dah 23 weeks, uterus dah besar dan berat, plus ligaments stretch untuk accommodate baby, so pressure kat back and sides tu normal. A few of my mum friends experienced the same thing, and honestly timing, posture, and gentle stretching helped a lot, try sleep with pillow between knees, avoid standing terlalu lama, and maybe try prenatal massage if boleh. But sakit yang severe ke terus-terusan, better check with your doctor just to make sure iya ligament pain ja, tidak ada other issues lagi.