Wa'alaikumassalam! Sakit perut masa 3 bulan mengandung tu memang biasa, tapi tu pun depending on what kind of pain lah, ada yang just stretching cramps, ada yang konstipasi ke, semua normal. A few of my mum friends experienced that jugak, mostly je it's the ligaments stretching as baby grows, tapi kalau sakit tu teruk sangat or ada bleeding ke, kena jumpa doctor cepat-cepat ye to make sure everything okay. Jangan tunggu-tunggu ja, better safe than sorry especially early pregnancy!