Hey guys!

I ended up with a pup last week that didn't get eaten and I decided I wanted to keep him. His eyes and ears were open, but just. So I've been feeding him Isomil per the instructions I read on a fostering website and he is starting to eat a little bit of solid food. He's been doing wonderfully until today. He's almost doubled in size this last week, but I've noticed that he doesn't poop as often as I'm used to rats pooping, and the last day or so they have looked dry when he did poop. Now today, his belly is bloated looking. I thought, "Oh no! Megacolon!" But I'm not sure. He is a red eyed white, about 3 wks old I'd guess, and even though he's bloated, his belly is very much squishy. Not hard. And he eats like a fiend! He seem to be constantly hungry today. If I flip him on his back and push on his belly (softly mind you) he squeaks a lot, but when standing if I push on his belly he doesn't complain.

So I guess my question is, is this Megacolon? Or something else? And should I be worried? Or is there anything I can do for the little guy?