What Is The Rib Pain That Comes At Night?

i have really bad rib pain it comes anytime from midnight and 3 in the morning and last sometime till 6 in the morning, i have looked it up on the internet and the only thing that is like that pain im getting is that of being pregnant but i know im not as i only come of my period yesterday, it is stopping me sleeping which is not good as i have a 4 month old baby to look after and its making it hard for me to cope as im so tired all the time