Wa'alaikumassalam! Aih perut keras tu normal je at this stage, dear, tu Braxton Hicks contractions, practice contractions lah! Banyak first-time mums dalam circle aku pun rasa yang sama around 29 weeks, takut je initially tapi baby tendang-tendang macam biasa je kan, so memang okay lang. Just make sure you rest, drink lots of water, and if it becomes painful or the hardening doesn't go away after you rest sikit, best la check with your doctor just to be safe!