Wa'alaikumassalam wa rahmatullahi wa barakatuh! Sayang, sakit perut bawah sebelah kiri masa trimester ketiga boleh jadi normal (round ligament pain, Braxton Hicks, baby position berubah), tapi sebab you're at 38 weeks, please go see your doctor atau go to the hospital today , better safe than sorry kan, especially since you're so close to due date. Dia perlu check kalau ada contraction yang teratur or any other concerns. A few of my mum friends went through sakit perut yang sudden dekat weeks akhir, and most turned out okay, tapi doc perlu assess properly je. Jangan delay, just go!