Sakit bawah dan belakang during pregnancy memang common, especially masa growing bump, tapi kalau sakit tu terasa intense atau terus-menerus, better check dengan doctor or midwife cepat-cepat ye, a few of my mum friends had similar complaints around 4 months and the doc just wanted to make sure everything was okay with baby and the ligaments stretching. Meanwhile, try pelvic support belt or adjust how you're sitting at work, leaning forward boleh aggravate the pain. Take care of yourself!