It depends
So at 16 weeks, my "bump" was still only noticeable to DH and I (I started telling a few folks@ work around 14 weeks, but other than the folks I told, absolutely no one had any idea until I was a good 18-20).
At 16-20 or so,my "bump" was weird/changed thruout the day...The only time it was even hardish, was right when I woke up in the morning. Then everything kind of puffed/absorbed food and beverages/bloated, and was much more squishy.
I'm 26+5 now, and have a proper firm little bump all the time (it's a joke with friends, family, coworkers - I went from barely there to "when are you due again?" in about 3 weeks)....but its still somewhat squishy after a day of bloating activity.
In terms of weight gain, have you been tracking? From what I've picked up most OBs aren't shy about commenting on it...I was a little overweight to start with, and my OB wasn't too shy about saying she wanted me to be very strict...I actually had fun "morning" sickness for that first 16-18 weeks and actually lost about 10lbs...which I've now managed to gain entirely back in the past 8-10 weeks :/