Perut mengeras masa pregnant tu normal je, especially kalau dah masuk trimester ke-2 atau ke-3, yang moms call Braxton Hicks contraction. Tapi since ni first time you're experiencing it dengan anak kedua, definitely check with your doctor or midwife to make sure everything okay, especially sebab dah 25 minggu. A few of my mum friends also had this, some lebih early, some later, tapi better safe than sorry, kan, doctor will give you peace of mind and confirm kalau just practice contractions atau ada apa-apa lain.