Sayang, perut mengeras dan tegang especially in first trimester boleh normal, tapi since ni pregnancy kedua, please check with your doctor dulu to be safe ya, better to rule out anything serious. A few of my mum friends said the same thing masa pregnant kedua because the uterus sudah pernah stretch before, so it might be more sensitive lah. Tapi jangan take chances, if it's consistent, painful, or ada spotting, pergi clinic atau A&E ok? Better peace of mind for you and baby