Im 18 weeks and hungry all the time too...ive only gained 3lbs but am a little overweight so my doc isnt concerned...ive popped out in the last week but this is my 3rd baby...everyone is different on when they start showing...one morning you'll wake up and won't believe how much you popped out lol.
Yes it is very normal..I'm four days shy of being six months and I still look every bit of four....which I wasn't even showing at four months....and I constantly eat myself lol