Uy, normal yan sa pregnancy, lalo na around 20 weeks kasi lumalaki na ang baby at umuusad siya, a few of us pregnant moms complain about the exact same thing, ang singit pain at pressure under the ribs talaga napakaachy! But since you're a first-time mom, mas safe na i-mention mo sa OB mo sa next checkup para sure lang na nothing else is going on, kasi better safe than sorry diba. Hang in there, mama!