Wa'alaikum assalam hun! Sakit denyut-denyut kat pangkal rahim masa trimester ketiga tu memang common, especially kalau ni anak kedua, uterus dah pernah stretch sebelum ni so sometimes sakit rasa lebih terasa. But since you're worried, better check with your doctor or midwife during your next visit ye, just to make sure everything's okay and untuk peace of mind lah. A few of my mum friends had similar aches dekat weeks ni and turned out normal lang, tapi memang kena confirm dengan doctor. Jangan stress sangat, your body's just preparing for labour, it's scary I know, tapi you've done this before so you got this!