The behaviour you describe in your first post is called guffing, it's completely normal. When newts surface they often take in too much air to sink back down so they'll float for a few seconds, and then release a bubble and sink back down.
Though newts don't get pregnant, they do get gravid: when they store up eggs before laying. Some newts do not eat when they are gravid; however, I haven't noticed this in chinese firebellies. They do get fat but going terrestrial is strange for a gravid newt.