Aiyo, sakit perut yang mana-mana bahagian masa pregnant memang boleh buat kita paranoid kan! At 20 weeks, perut memang boleh mengeras sikit-sikit (Braxton Hicks boleh start awal untuk some of us), tapi kalau sakit tu intermittent je and takde other symptoms macam bleeding atau spotting, likely normal lang. A few of my mum friends had the same worry around that time, turned out just ligament stretching. That said, better play it safe and check dengan your gynae next visit ke or call them if the pain becomes consistent or worse, sebab first baby memang la nak make sure everything's good!