Wa'alaikum assalam! Sakit pinggang dan perut senggugut tu memang common dalam 6 weeks postpartum, lagi-lagi kalau first child dan mungkin banyak bangun malam untuk jaga baby, tapi sebaiknya you check with your gynae or doctor just to be sure, especially kalau sakit tu getting worse or ada bleeding pulak. A few of my mum friends experienced the same thing, and most of them it was just dari recovery + exhaustion, tapi better safe than sorry la. How's your bleeding, and are you resting enough?