Wa'alaikumassalam sis! Sakit bawah perut masa early pregnancy tu memang common, tapi sebab baby first and you're only 15 weeks, better to check with your doctor dulu okay, especially kalau ada lenguh pinggang and susah nak bangun, sebab dia boleh confirm everything is fine and rule out anything yang perlu perhatian. A few of my mum friends had the same worry at that stage and their gynae said it was ligament stretching, tapi tiap orang beda-beda so jangan ambil risiko! Kalau boleh, go in for a check this week just for peace of mind, better safe than sorry, especially first pregnancy kan.