Alah normal je lah, around 20 weeks baby dah jadi heavy and your ligaments start stretching to accommodate, so rasa berat tu memang biasa! A few of my mum friends also complained about the same thing during mid-pregnancy, one of them said she felt better with a maternity support belt, boleh try. Tapi kalau the heaviness or back pain jadi worse or discomfort tu extreme, better check with your doctor just to be safe kan, even if it's just to get some reassurance and maybe physio tips untuk ease the pain