Aww congrats on your first pregnancy! Perut mengeras tu normal saja, especially around 19 weeks, a few of us experienced Braxton Hicks contractions (practice contractions) around this time, tapi sebab first baby kadang we get paranoid jugak lah hehe. That said, sebab this is your first time, best you check in with your doc or midwife just to make sure everything's on track and to put your mind at ease, okay? They can assess and give you proper peace of mind!