Eh, I think you should really check with your gynae about this one, because a small belly in pregnancy can mean different things and it's best to get it checked properly lah, my one friend kena worried gila-gila about this until the doc explained it's all about how the baby is positioned and the amniotic fluid level. There's no real "tips" to normalize it yourself, so do pop by the clinic soon just to be sure everything is okay with baby and get their proper advice!