Alhamdulillah baby okay lah, tu yang penting! A few mums in my circle pun ada experience macam ni around third trimester, sometimes perut nampak smaller or weight gain slow down tapi baby still growing fine, especially kalau baby position berubah or amniotic fluid normal je. Since your doc sudah confirm everything is good from the scan, try jangan worry sangat lah, tapi make sure you're eating enough nutrients and staying hydrated ye, sometimes mums tak realize they're not eating as much sebab perut dah penuh or busy preparing for baby. Keep monitoring weight gain next appointment, tapi sounds like you're doing great!