Oo, normal yan first-time mama! Yung pag-harden ng tiyan (Braxton Hicks contractions) usually nagsisimula around 6 months but mas obvious pa towards the end ng pregnancy, lalo na pag stressed o active ka. A few of my mum friends said it was scary at first kasi parang may nangyayari, pero it's just your uterus practicing, di pa yung labor contractions.
Just make sure to rest, stay hydrated, at kung sobrang painful or may bleeding, go see your OB na agad para peace of mind mo!